Download The Fairlight explained
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TIf,E E'ATRTTGIIg EXPEATSUED When the Fairlight CMI was released seven years dgo, both the machine and its software represented a significant step forward in the application of computer technology to music. Today, the Fairlight is used in the rnaking of popular music the world over, as well as performing an important role in the field of musical and technological education. Despite this, very few people are fully aware of what the CI}II does and how it does it. Jim Grant, who's been working with one for a number of years at the London College of Furniture, has decided to rectify matters by writing a series dedicated to explaining the Fairlight's workings. Part one appears below. E & MM AUGUST19 84 efore the Fairlight'sappearance, most computer music systems were the perogativeof mainframes and th e i r c ont r ibut iont o th e w o rl d o f everyday music was slight. Kim Ryrie (the Fairlight'sfather)and his Australian colleaguessoon changedall that, however and their inventionis now used in almost area of music production,to the extent that many people appreciateits sound without realising that they're lis te n i n gto ' m us ic by num b e rs ' . However,despiteits widespreaduse, thereare relativelyfew Fairlightsin general .100 circulation- less than in the UK and to see one in actionat close quarters is a realtreat.Hereinliesthe rationalefor this series of articles.What does the Fairlightdo? How does it do it? And what can the averagemusiciando with it ? 0r , 1il8N n Software A foolproof system of connectorsand a quick glanceat the manualon the part of the user- ensuresthat the Fairlight can be powered up in no more than five minutes.The VDU displaysthe expectant m e ssa g e' CM l RE A DY ' ,w h i l e th e C PU hums quietly:thereare threefans pulling air throughthe innards,keeping500 watts of power dissipationdown to an acceptabl e te mp er at ur e. . . . lnsertingthe Systemsdisk in the lefthand drive(Drive0) resultsin a faintclick as the stepper motors engage. The operating software is loaded as a series of 'fetches'- each section of program loaded pulls in the next section.When this process has been completed,the user is faced with the Index page. See F i g u re1 . Here lies one of the Fairlight'smost powerfulfeatures.The whole system is menu-drivenand the differentoptions correspond to different VDU displays and sets of commandswhich are entered from the alphanumerickeyboard.Each option is referredto as a Page. A Page has one or more files resident9n the Systemsdisk which are loadedwhenthe Page is selected. Page 1 is the Index Menu itself (Figure 1), while Page 2 managesthe files stored on the disk in the right-handdrive(Drive1).Thesefiles are user-created, and there are seven differenttypes, as indicatedby the suffix afterthe file name.Theseare as follows: NAME.VCis a voicefileoccupyingabout 2OkBytes.lt holds waveform data (1610 and extra informationregardinglooping and so on. NAME.CO holds control information such as portamento,vibrato frequency and depth. 28 rnbL < rNbL J PRGE4 PIi|jE 5 f I|1 IRLI [ HT n l - 'L b PBriE 7 P R I J ED PFDE S PH6E FI PBl]E [, PFEE D PBriE L PrirlE R I l,l.I u3 , t 5 , Rl , l l TN b L 5 I.JS E R N FI14E, J I l l Hardware To take deliveryof a Fairlightleaves your bank balanceempty and your living room full. The hardwareconsists of a Central ProcessorUnit (CPU),one - or optionallytwo - six-octavekeyboards,a typewriter-styleQWERTYkeyboard,and a VDU with added lightpen.ln addition, there are some long connectingleads,a Systemsfloppy disk drive and a box of disks containinglibrarysounds. INDEX DISK DONTROL K E Y B D H R DC O N T R c l L I I I I R I '1 OI C N ENUELDPES I , I E U E F O RE I l E N E R B ITO N I , I H U E F I ] R I I'1 R f i I ,I IN C c c | N T R | | LP F R R I l E T E R S S | J U N DS R I l P LI t I | ] SEUUENDER f f N f f L O GI N T E R F H I E C O I 'I P O S E R l , I H U E F O RD HI S P L F I Y DI S K L I B R F R Y R E R L - TI I l E C D 1 4 P | ] S E R S C R E E NP RI N T P IID E I DRRNT l@t 011f lf f t i D ' DI SK, E X E I l P L E USER. J I T '1G R f l N T 1 I NU E N T . I N I6 2llit r I lE r m t7 3 PRE L U D E, I N I8 4 UI U F L D I , I I I I9 5 Bf iS S G T . U C ? B 6 BDD 2 UC 2I 7 CBE L L O ( ] [ U } C E2 8 G RN G S R U C 2 3 S STIC K .UC 24 1B STR I I'ID UC 25 UC 28 11 I f r N N T2 ERS S G T C O 2 7 13 BBD z . . .C0 28 14 CBE L L O O O . C O2 9 I 5 G RN G S R . C O 3 6 FREE SPHCE. LIBRffRY NO. STIDK C|] ItiuENT .S0 P R E L U D E. S O UIURLDII.SO LOCUST .RS PBGEI .PX PFGEz .PX PFGES ,PX SYHTH .PC SYNTH . PT BFSSD .SS CNTRL .SS .SS SN3 TUHEl ,SS TUNEz ,SS I l U L TI TRBNS F E R 536 8 DELETE EUERY !.qgH$I .,-l|:| .tvee:-ln$IRU|]1ENi v o i c e s 'B D D 2 STICK clt r CIi N D EL EII tlcL , 24. . .,, ,ye| l, ..:i,,r,e BFSSGT STR|4 ID T l@ Com'irter rcthsb@rd Address bus Cmlfol crrcurlry wovelorm RAM dio signol oulpui AUGUST1984 E&MM IfIIiIIEIIIIE and types F fim SPRCE o n d isk lfnfilfli$ number { t4 UL T I & C B N C E L) EfiffilflIn tile s flllffiE u se n o r f i ]e nenret d isk, co m m a n d EIIfII fi l es EN:III| IE in stn u m e n t o n vo ir e f ile s m l!fiflIn in str u m e n t I[ll| ifflE vo ice f ile s ]m :filfln f ile s sEq u e n ce |lJifllfll somnrend If#IIEiIfE cor'mahd pnotect nFffiff:dmftfmlfi i on Im m L Ef0 o r r m tsste r k e yb o sr d m fiil:Im sh o r tcu ts 2 sheet, 3 3. 3 4 c f 6 b 7 6 I 1 8, it toucn sny l0 X r ^ r ith L IGHT PEN o r t ouc h lI f f i type, u h erE : or t vP e ' n(set) = n sneel HI ( n e t u r n ) Pa g e2 Co m m a n ds EE!tr4 TRfiNSFER FILES T O BNOT H , YPE. L I GHTPEN (select files) T,file (retu nn ) <T R f i N S F E R ) or T, f ile, f ile, l ile( , . . et c ) ( r et ur n) = FiLENEI I E SF or r,rhene , file * * - *l or I f* or (s s m e as DELETE; s ee abov e) E X RI'4PL ES, T. CH0RUS,I N( r et unn) T, 4-1 8, FBLE. UC,2S( net ur n) F i Ies u i I I b e copied FR0l' 1dis k in RH dniv e ( D I S K f i ) T 0 a n o t h e n G iv e TRRNSF E Rc o t n m a n du i t h s v s t e m disk in LH d nive ( DI SK B) . l,lhen the messaEe' disk in LH d nive and DI SK R in RH dr iv e. PL RCE FI LE DI SK I N LH DRI U E l, lhen t h e t n a n s f e r is E pp €tsFS, p lace D I SK B in LH dr iv e. m es s age r r i I I neques t t h e r e p l a c e m e n t o f t h e cornple ted a fin al If a f ile alneEdy ex is t s on D I S K E ( h a s s e m E system d isk. N0T be ovenunitten name a nd suf f ix as f ile on DI SK R) , it ui l l you n con s ent . See als o PROTECTION. wit ho ut TYPE, T, t ( net ur n) l,lhe n the me ssege eppeEr s plac e a EEI I t r f i 1 e d i s k i n L H d r i v e . Ne r *rd i s k u i I I u s u a l l y R epla ce syste m dis k r , r hen c om Plet ed. shor.r an incne ase in FREE SPFCE av ai lable @ NAME.INconfiguresthe CMI to a particular instrumentstate. Voices are automaticallyloaded and spread across the keyboard. NAME.SQ holds polyphonic keyboard sequencerinformation. NAME.RSis a realtime sequencer(Page R) file. NAME.PXcorrespondsto a screendump (Page S) to disk. This can be spooled later to a dot-matrix printer for hard copy. NAME.PC,PT,SS are MusicComposition Language (MCL) files. These are generated on Page C and hold text files that describenotes with duration,dynamics and so on. A voice file can be loaded in a number of ways. Probablythe easiestis to point the lightpenat the volce name and then at the command LOAD at the bottom of the display (Figure2). Drive 1 springs into action immediately,and after a secondor two the selectedvoiceappears on the keyboard. So far so good. But where does the voice informationgo, and how does it result in a sound when the kevboardis played? E&MM A UG US T 198 4 channel cards perform this function The computersectionof autonomously. the Fairlightpassesparameterssuch as pitch,vibrato,portamentorate and looping points along its data bus, and once these have been received,the channel card outputs the sound until the parameters are updated. Overallpitchingof the CMI is determined by a systemclock residenton a soecialcard known as the Mastercard. We'll be referringto this on numerous occasions over the next few months, since it holds the circuitry for a good many of the CMI's functions.A 34MHz oscillatoris onboard,and this is divided and fed to the individualchannelcards. It's from this clock that the RAM clocking rates- and thus keyboard pitches - are generated.The wholeinstrumentcan be tuned by scalingthe masterclock. GhannelCards Insidethe Fairlight,thereare usuallyat least 16 circuit cards, the exact number depending on various options such as an analogue interface and sync card, and eight of these are known as voice or channel cards. The Fairlight produces sound by a processcalledWaveformSynthesis.Each command that deals directlywith sound generationmust involveat least a section of a waveform. The waveform itself is held in 16K of RAM on each channel so card as a direct digitalrepresentation, that increasing amplitudes give larger binary numbers. Therefore, when an eight-note polyphonicsound is present on the keyboard,eachchannelholds the same voice data. Put simply, the channelcards can be regarded as digital oscillators whose waveformis determinedby the contents of 16K of RAM (Figure3). Differentpitches - as playedon the keyboard- conespond to the MM"information being read and converted by a DAC at differentrates;the Lookingagain at Figure 2, there are severalcommands at the bottom of the display.TRANSFERallows files to be copied from one disk to another,using Drive0 as the destinationdrive.This is essentialfor creating backup copies of importantmusicand/orsounds.DELETE erases unwantedfiles to make room on the disk. Invokingthis command prompts a confirmationmessage to prevent accidentalerasureof importantfiles.When a file is deleted,FREESPACEincreases by the deletedfile size. At the very bottom of the displdy is an exampleof the QUERYcommand.This tells us that LOCUST.INfile will automaticallyload eight voices, whose names are shown. Help Pages By this time,you'reprobablywondering how anybody using a Fairlight ever managesto rememberall the commands, especiallysince we've only considered Page 2 and there are another 13 still to go. The answeris simple:Help Pages. Figures 4 and 5 show examples of Page 2 Help Pages. In fact, the entire user's manual is held on the Systems disk.and sectionsrelevantto the current display Page can be inspectedat any time by typing HELP(what else?). Initially,an index sheet is displayed (Figure4).Touchingany of the highlighted options with the'lightpenresults in the Help sheet specificto the selected option being loaded and displayed. The user can flick backwards (BWD), forwards (FWD)';or recall a previous place (PRE): commandscan be enteredfrom the Help sheetswhile viewingtheir correct format. The CMI then automaticallyreloads the display page that called the Help sheet in the first place, and executes the command.And yes, there are even Help sheetsthat explainthe use of the Help sheets.. . . That about wraps up the first part of what will doubtless become a saga of some duration. Next month, we'll take a look at Page 3 - the keyboard map and the waveformdisplay page, Page D. Jim Grant E&MM 29 TIIE T'AIRLIGHT E)KPEATTUtrD The secondpart of our insightinto one of the world's most popular computer instrumentslool<sat displaypagesand what they tell CMI owners.Jr* Grant ast month we describedthe general software conceot of the Fairlight and how much of its powerlies in its abilityto presentits functionsto the user as a group of related files called Pages.We saw that the CMI poweredup with the Index Page (Page 1) and that soundand music fileswere managedby Page 2. One of the oroblemsassociatedwith most sound-generatingequipment is the way in which the sense sight is excluded from the orocess of sound formation.Most instrumentsoperateon =--*.u+'\\S..S*\ \\R '\\- N \.\._> inLrL;,{ rlll|1Hfitr .IUII-L .:RUIlF ET fl lIrE lltsuEFrJPF Ir Ir:,FLtii' l,,.lltil;f, 4 1 T t:t_ll,tFT,t tJi i t,l E Fr :r Ftt1 Ir I:iF LtlT F r:rt'l ''1 H T ,HE tliil litlj--ffEl B6 l'1t-tIt E , E;4 :ii !l-El- L E- + ir I S E P T E M B E1 R9 84 E&M M the basis of the user twiddlingthe controls and stabbing the keyboard. Fair enough: of all our senses,the ears are by far the most acute. Yet if we consider all the electronic music equipmentcurrently available,the most user-friendly instrumentshave graphic displays,perhaps in the form of panel legendsand LEDs or liquid crystal display. Despite the fact that sight is a very poor qualitative sense, it can be of enormous psychologicalhelp in our field.Basically it boils'down to: 'lf I can see it. I can understandit.' nel allocationand keyboardmaps. Figure5 shows a typical displaywith eight separate voices loaded into the CMl. RegistersA to H are groupsol one or more of the eight Ch.annelsand 'NPHONY'is the numberof notesthat can be played with the sound held in a Register.A quick look at Figure5 reveals that there are eight active Registers, each holdingthe voiceindicated.In this case, all eight Channelcards hold a unique sound, and therefore the maxirhum number of notes that can be played on the keyboard with any single sound is one. This is indicatedby the corresponding'NPHONY'. lf a single eight-notepolyphonicvorce is required, only RegisterA will be activeand Channels 1 to 8 will be allocatedto A. The active Registersare mirrored on Page 2 so that they can be loaded with sounds from disk. The Fairlightwill flag an error T EU H PET f4 u l r E, 4 I,IFU TFD R I'1TII i ;P LR Y :J.r D^ ^^ r-\ r d.Bu, u There's no doubt that the Fairlight's visual presentation is founded on this premise.Each display Page is graphic withoutbeingostentatious, and PageD, the voice waveform display, is a prime exampleof this. Typing PDfollowedby a keyboard RETURNon the alphanumeric will resultin a displayof the type shown in Figure 1. To appreciatethe significance of the display,we must delve a little deeper into the workingsof the C MI. Rememberthat voice informationis held in 16K of RAM on each channel card. To simplifymatters,the CMI divides the memory (and thus the waveform) into 128 sectionscalledsegments. Each segment consistsof 128 bytes,so the waveform comprises128 segments multipliedby 128 bytes to give 16384 bytes,ie. 16K. This savesthe musician handling unwieldy computer numbers when dealing with the waveformRAM. The display shown in Figure 1 is a psuedo-3D representationof the voice called TRUMPET.Each line from left to right is a segment, and the foremost segmentrepresentsthe beginningof the sound. When a keyboard note is pressed, the CMI reads out the RAM information segment by segment from the front to the rear of the display. There are two display formats,A and B, and a numberof optionswithineach type. Figure 1 is in formatA, and segments1 to 128 are shownin stepsof 4. Figure2 is againformatA, with the end segment number 32 and steps of 8: thereforeonly five segmentsare shown. Format B gives an oscilloscope{ype display,but with each segmentslightly above the precedingone. Again,there are a numberof displayoptions.Figure 3 shows TRUMPETsegments1 to 128 in steps ot 2, and Figure4 segments1 to 64 in steps of 8. AlthoughPage D is purelyfor display purposes and does not support any sound creationcommands,it's still an invaluableaid. At its most basic level.it answers the ouestions'where has the sound gone?' and 'is the waveform zero?'. l\^ rage 5 Page3 is anotherutility-type display Page.lt dealswithvoicetunings, ChanS E P T EMBER 19 84 E&M M STEP.l E 4 INIlEX 0 l' ll,lffN Ir, fi 5 t' D E F G H I I lIr!a 2 i Sr I Cll 3 ) BH5:,r.iT { i STRI,I I II 1 5 I 'S T F ; 1 4 I D 2 6 r c8ELL00q 7 ) TffNN P I rlHNr:SF :l ,l',1i{::rTEF: E .!JLffUE FITr::H, l?U si:FLE, t(lT a 'j OHHfiND ' SHXY SNfiRE BDRU14 ORGtiN Lg25 886 ?,48 BAVJ 3 .I,lFSTER 6 .SLFUE PI ICH' I28 SCFLE, l ? r -:; V <.U U MUSICIAN OMPUTER message if you try to open another R e g is t eror inc r eas eth e N PH O N Yb e y o n d e ight .A s im pler u l ea p p l i e sth : es u m of the active Registers times their NPHONYmust be less than or equal to eight. Figure 6 shows another exampleof the Registerallocations.Here, another set of voices has been loaded.so the NPHONYand Registersare configured differently.Although the Registerand NPHONY settings may seem a little confusing and limited, the exact configurationis determinedentirelyby the musician,and changescan be effected very quicklyfor evaluation. Keyboards andTuning Any voice can be tuned in increments of plus or minus one hundredthof a semitoneup to t6 octaveswith crystal accuracy. Scale allows the Western temperedtuning of 12th root of 2.00 to be changed to any other macro/micro tuning,eg. for quartertones,you simply changeScaleto 24th root of 2.00.Pitch is a master tuning control which can vary tuningof all the loadedvoicesby a quarter of a tone in 256 discrete steps, to bring the CMI in tune with other instrumentsif necessary. The KeyboardMaps each consistof a keyboardnumber (1 to 6) followedby six lettersindicatingthe Registerassigned to each octave.As the C[/l is a musician's instrument,it supports two sixoctavekeyboardscalledthe Masterand the Slave.Usingthe maps,it's possible to create eight differentkeyboardconfigurationsby choosingwhich sounds will play on each octave within a keyboard. The Master and Slave can be linked(as shown in Figures5 and 6) to any map by changing the Selection numDers. Theinformation presentedin Page3 is knownas an Instrument file.The filecan be savedon the user disk and is given the suffix NAME.IN.When this file is loaded it will pull the specifiedvoices into the CMl, allocate the Registers automatically,adjust the tuning and spread the sounds across the keyboards. Instrumentfiles are a usefully quick way of bringingthe CMI up to a playablestate with 'preset'voicesand tu n i n g . rt I 11arcware At the timethe Fairlightwas designed, the microprocessorwas consideredto be a medium-to slow-speeddevice.To increasethe power of any computing system, designers have two basic choices. Oneof these(theSynclavierapproach) is to base the instrumentarounda discrete logic minicomputer, thus utilising the raw speed of logic chips. This is qui tean el egantsol uti onsi n ce'm usicby numbers'requi resl ots of num bercr unching, but the other choice, and one w hi chi s becomi ngi ncreasingly popular , rs computrngconcurrency.In a basic CMI system, there are four microprocessorsof the 6800family.Two of these i e. one each in t he are i n peri pheral s, music keyboardand the alphanumeric keyboard,and this meansthere can be several independentprocesses being executedconcurrently. The microprocessorin the alphanumericscansthe keys and passesthe data to the music keyboard when requested.At the same time, the music keyboards are scanned for pressed notes,key velocitiesare calculated,and the controlslidersand switchesread. At the right-handend of the Master keyboard is a calculator-stylekeypad and alphanumeric displayused for rapid loading of voices in a live situation. Music keyboard information has the highestpriorityof all data in the CMl, which respondsinstantlyto the packets of data sent flying down the cables at 9600 Baud. Well that about finishes off our descriptionol the utility-typedisplay PagesIn case you'rewonderingwhat the Mode settingon Page 3 is for, don't worry: all will be explained. Next month, the controls on Page 7 r and samplingon Page8. MUSICIA OMPUTER TIIE T'ATn.LTGIIT EIKPEATTUED Partthree,anda discussion of how the CMI samples a soundandwhy its own particularsampling techniques are employed. Ji* Grant t last we've coveredenoughof the CMI basics to concentrate on the more , \ interestingsoundcreationPages.Now, the single feature that characterisesthe Fairlightin manypeople'smindsis its abilityto sample natural sounds: this aspect is dealt with by Page B, and is surprisinglysimpleto A /.\ than can be looped is known as a Segrpeit Here lies the crux of choosing a suitable SampleRate.lf we attemptto loop a Segment or group of segmentsthat doesn't contain a whole numberof cycles,the 'ends' of the loop won't join up withoutcausinga suddenlumpin amplitude.Choosingan inappropriatesample resultsin a short sound when the samole is played on the keyboard,and this becomes shorteras we ascend the octaves.To overcome this,the Fairlightallows sectionsof the waveform RAM to be read out repeatedly (or looped)as the key is held down, thus sustaining the sound.The smallestsection of RAM USE. At the rearof the CMI liesa selectionof line and mic inputsto suit most applications.That about takes care of the hardware.because everything else is dealt with by software. Typing 'S' or touching 'Sample' with the lightpeninitiatesthe samplingprocess.Aftera second or so, the Display box shows the sound envelopefor quick monitoringof input levels (see Figure 1). lf all is well with the Keyboard Maps on Page 3, the sampled soundwill be playableon the musickeyboard. So far so good. But what are the other functions for? Well, some of them are selfexplanalory. Sample Level is a softwarebased volume control and can be used to attenuatesignalsthat exceedthe input range of the Fairlight.Unwantedfrequenciescan be reiected by using digitally-controlledhighpass and low-pass filters:their cutoff points are set by FilterHighand FilterLow.Theactual circuitryliveson the ubiquitousMasterCard, and takes the form of switched resistor networksusing the much-lovedCMOS 4051 chio. Whenevera signalis convertedto a stream of digitalnumbers,it's necessaryto bandlimit it to one half, or less, of the Sample Rate. Statedsimply,this meansthat we musthaveat least two samplevaluesof the input signal's amplitudefor the highestfrequencypresent.lf this conditionis not met. the informationthat the sarnpling process has captured is not sufficient lo reconstruct the original signal without frequency distortion. This type ol distortion is known as 'aliasing'and is both extremelynoticeableand rather unpleasant. The CMI guardsagainst'aliasing'by incorporating tracking filters controlled by the SampleRate. SampleRate Althoughsamplingitselfis verysimple,and impressive results can be obtained very quickly,it's well worth the troublespenrjing some time adjusting the Sample Rate to a valuethat suitsthe pitch of the input signal. imporrant aspectof theCMrthatobtiges usro payattentron r.u^t:^to thecorrecr^:T?1"^ is The number of original samples taken ,^ fixed and equalsthe length of the waveform RAM,ie 16334.The fasterthesesamplesare taken,the shorterthe durationof the sound becomes (althoughthe fidelity increases).This 86 U D Ir - 'E, I I'rHFiI l'1:1 0 t' ll' ll i N Ir, :l r-rl _l H DtH l 'l FL I H rJ S R I'IP LE FTIi TE FILTE R LI:II,I FILTE R H IGH Ii t'l FFrE i gr:rFi Zv I EB Hi I E I 'F F E H I,IP LE LE U E L TR I GI]E F; LE U E L TFIII-;i j E FI TIE LB \. c::. : E tl i S fi I'IP LE IIIS P LFIY Figure1. I ilt t : , R TU N E l 4 0 D E, 4 Ul' 1l( l l i {It, I , ] F U E F | ] R I!'II 9 P L H Y Figure2. | I ll IrE:i r-rtlt1Hfl Il lt I l-t IiFtfii U i J IU E . 'l MLx'i . l ,l H rl l E r-1Frl F tr FIFJ'1Fi T+ 11Ir ::iE t:; 1 L Tt- tt{E l l D Ir E, .{ ::r? 5TEF, I ffili,iii?Fr [l:liili.#, llii',:;ttlj,, :-. r' --rli./ l--ts [,1]lll'*ni:L1:----.= .,' L''Figure3. OCTOBER1984 E&MI I OMPUTER MUSICIAN 1 l rate resultsin a dreadfulglitchwhichincreases at a rateproportionaltothe pitch playedon the keyboard, lf the sample rate is almost right, a one-segment loop produces a sudden slight pitch shift, and waveform crests and troughs 'drift' laterallythrougha PageD display.This is shown in Figures2 and 3, where a drift to the right (sharp)is caused by the sample being set too high and a drift to the teft (ftat)by it being too low. Figure4 shows a sound which is in tunewith the system and therefore loops perfectly. At the other end of the scale, if the sample rate is totally wrong the display becomes a hopeless jumble (Figure5). The relationshipbetweena whole numberof cycles and each segmentof waveform RAM is also the relationship required for a visually coherent display. Thus samplesthat look good will inevitablysound good, too. Now, if all this sounds rather complicated and you're beginningto wonder how anyone gets anywhere near choosing the corect sample rate, then take heart. lt's all in the help pages for Page 8 - see Figure 6. A useful sample rate table is included,and with a little practice it becomes quite easy to arriveat the conect setting within the space of a few trial samples. conect clocking rates requiredfor digital{oanalogueconversionwhen a keyboardnote is pressed. However, for the duration of the samplingperiod the CPU grabs Channel 1, and forces it to produce a streamof pulsesat a frequencyof 128timesthe samplerateshown on Page8. This is suppliedto the ADC, which resides on the Master card, and once the samplingprocess is finishedthe CPU restores Channel1 to its originaltask. TriggerLevel is the amplitudethresholdat which the sampling process is triggered to begin.When the Sample command is given, the system waits until this level is reached before proceeding.Once the threshold has been exceeded, it's possible to delay the conversionby using the TriggerDelay,which has a rangeof 0-65533 milliseconds. Thiscan be especiallyusefulwhen samplingfrom tape, for example,as a tone burst can be recorded shortly before the signal to be sampled and used insteadofthesignalitselfto trigger the samplingprocess.Trigger Delaycan then be used lo define the precise point at which samplingwill actuallybegin.This is extremely usefulfor soundswith a gentleattack such as slow strings. Lastly,the Compressoris a softwareswitch which controls a hardwareoption. Basically, this turns the conversionprocess into a nonlinearsystem,thus enhancingthe dynamic range.The electronicsuse the same type of circuitryas that in manyanaloguecompanding systems. However, very few Fairlights are fittedwith this option as it can have a strange effect on the commandson Page 6. Well, that about wraps it up for Page B. Thereisn't room this monthfor a discussionon Page 7, so we'll have to leave that for next r month. IiLEi; I tr lJ8 ilIl IT U I I L l , l S u E F r t P i Il r I : : F L f ri , .l ADC The actual analogue-to.digitral conversion is accomplished by a 10-bit converter, even though the CMI is an eight-bit machine.Only the top eight bits of the sample values are stored, while the two LSBs (Least Significant Bits) are ignored.This improves the linearityol the conversion, which means that the signal step size required to cause a conversionvalue to change by one LSB is fairly constant over the range of the ADG. / The relationship between the amplitude of the input signal and the sample values generated is linear. When the signal level changes by a given amount inespective of the absolute value the conversion code always changes by the same amount. This is where the Fairlight differs from most other sampling machinessuch as the Emulator.That uses a non-linear conversion method (called 'companding')which allowsmore codesto be generatedfor small signal valuesthan for large ones. Whenever a signal is represented by a finite range of numbers - in this case f255 (eight bits) - two things suffen noise and dynamic range.The noise is only heardwhen a sampled sound is actually being played through a DAC, ie. the ADC and DAC are not in themselves inherently noisy. Making sure that the peak ol the input signal causes the maximum ADC code to be generatedensures that most of the noise is masked by the volume of the signal on playback. The Displaybox in Figure1 is an invaluable aid in this respect. Dynamic range, on the other hand, is a measure of the range of different amplitude values that the ADC can handle. In a linear system, this is directly related to the numberof bits used in the process and, roughtyspeaking, the dynamic range of the sampled signal is 6dB times the number of conversion bits. Since the Fairlight uses eight bits, this gives 8 x 6dB = 48dB dynamic range. Companding techniques result in a larger dynamic range (about 70dB)forthe same numberof bilsused, but at the expense of greater noise at low signal amplitudes. The reasons for Fairlight's choice of a linear converter will become more apparent when we look at the functions on Page 6. The actual sample rate is very cleverly generatedon Channel card 1. Normally,the onboard circuitry is used to generate the E&MM OCTOBER1984 Figure4. I't I 0 l' ll' lF NIr' JTUNE t '1 0 0 E' I,IITUEFcJR DI 'IS F L R Y 4 F|:l R I'18T.F noi e E c E F S ffI,l P LE R Il TE 9 +gvts 14817 15884 1 8 7 4 4 ', 17748r r sTss tsst2 2I BSB 22351 ?3EBB 29S35 32 -E vr S T E F '1 2 -tE : ,"'i 74SS TiiEr! Er:r7e 8r:rlB 3337 iig5E 1Erg49 3?t3 : j B 5I 4 I FE 4 4 : {5 4EtS 4 S 7 'i l 5 t 7 '{ I i i ,,:,,1 I I I i, lltr4El I U5 4 4 t3t38 i SrllF Etr? EE45 6l u..:=; THE EATn'LTGHT fi t E tr)KPEATTUtrD just How the CMI providesfor specialeffectsandlooping- in a language about everyonecan understand. Ji* Gra,nl ast month we dealtwith one of lhe I Fairlight's main sound creation I L methods:sampling.The simpleact of pointing a microphoneat a sound sourceandtyping'S'on thealphanumeric keyboardtransformsthe Fairlight froman expensive computer into a powerful musical instrument.And the keyword hereis 'musical'.Theabilitylo createnew and interesting sounds(orindeedsample them) is not in itself enough.What is requiredis controloverthatsoundand,to coin a popularphrase,the controlmust be real-time.Musicians,of course,call this control 'expression',and it's a particularlydifficultfeatureto build into a computer-basedmusicalinstrument. Consider a typical case in which a Fairlightusermight be playingthe music keyboardwhile listeningto a sequence pre-recordedon Page 9. Everythingis running smoothly: the CMI is reading sequenceinformationfromthedisk,sorting it out, and sendingthe data to the voicechannelsto be played.At thesame time,the musickeyboardis beingscanned for pressednotesand moredatasent to the channel cards: notes are stolen if necessary.Next the usermay decideto swell a parlicularvoice by movingthe appropriatefootpedal.Here the CMI is forced to deal with an asynchronous event in the normalproceedings, so the pedalvaluehas to be updatedconstantly and the valuesobtainedusedto scalethe amplitude of the voice throughoutits duration.And if thiswerenot enough,the Fairlighthas 17 parameterscapableof being controlledin real-time. It's t he unus ualm u l ti -o ro c e s saorc r hitecture of the CMI that enablesit to handle so many asynchronoustasks si mu lt aneous ly , l e t' smo v eo n to l h e but presentation of thecontrolsandtheiruse. D^ - ^ rdtc -l / Al l t he c ont r olsar eh a n d l e db y P a g e 7 , and a typicaldisplayis shownin Figure1. The page featuresall the usualcontrols associatedwith processingsound:each of the eight voices loadedcan have its o wn uniquec ont r ols e tti n ga n d c a n b e sa vedt o dis kwit ha c h o s e nfi l e n a me and the suffixCO.Whena voiceis loadedinto th e CM l, it will pull rn a s p e c i fi e cdo n tro l fileif it was previouslyLinkedto thevoice, u srngt he c om m andL N K. At t he bot t om of t h e d i s p l a yi s a b o x which indicatescurrenlly-loaded voices. Th egont r olfilem ayh a v ea d i fl e re nnl a me from its intendedvoice so the two are drfferentiated visually.Theactivecontrol fi l e is t he nam e hi g h ti g h te d w h i l e th e active voice is shown in the top righthand corner.Other controlfiles can be inspectedby pointingthe lightpenat the names in the displaybox or by typing ' V .n ' .where' n' i s the voi cenumber. Thereare six real-timefadersand five switchespatchableto most parameters. Threieof the faders and two of the switchesare on the left-handside of the music keyboard,while the other faders (orfootpedals)areaccessiblevraCannontype connectorson the rear of the keyboard. In addition,the music keyboard resultsfrom its use. The Filteris a lor'.,pass tracking filter resident on each C hannelcard, used to at t enuat eanv unw anted hi gh-frequency cont en: present in the voice: the cutoff f requency is raised by simply increasing the val ue.l t' s al l real l ya case of svr ings - a hi gh f ilt er set t ino and roundabouts gives a bright realisticsound but often w i th di gi tal bi rdi es w ar oling in t he background, while low filter values suppress any funnies but reduce the soundto a dull noise. When Portamentois on, each Channel allocatedto the voice produces a continuousglide between each nei.,' pitch it is to play and the last pitch played,the rate of note glide being set by the Speed control. 'Glissando'drffers from Portamento in that the glide is not continuousbut chromatic, and all the notes on the keyboard between the stad and end notes are played. lf both Portamento and Glissando are selected, Portamento takes precedence. 'Constant Time' is a switch which selects between two types of glide: when it's turned on, the same time is taken to travel any musical intervgland the rate of change alters ac_cordingto that interval, hence the name 'ConstantTime'. This results in polyphonic portamento or glissando. in which the notes arrive at their destinationsat the same time producing a coherent chord. With the switch off, the rate of change remains fixed (determinedby Speed) and the time taken to glide varieswith the size of the interval. passes key velocityinformationto the CMl, and this can be patchedto Level and Attack as KEWEL. Below the voice list in Figure1 is a comoletelistof thecontrolsandswitches that are available. Thisis usedin conjunction with the lightpenand providesa quick way of patchingthe controlsto vai'iousparamelers:thelightpenis pointed first at the parameterand then at the The Attack parameterhas a range of controllist. A patch can also be estabzerol o 16,384mi l l i seconds, and m ay be lished by tabbing a cursor around the patchedto 'KEYVEL'for touch-sensitive displayusingtheQWERTYkeyboardand controlof the attackti me.lt 's act iveonly typlngin the appropriate nameor numeric for Mode 4 sounds, and is extremely value.Figure2 showsone of the 'Help' usefulfor imposinga degreeof artificial sheetsfor Page7 whichprovidea quick ' enveloping uponsampledsounds.'Dampreferencefor the range and possible i ng' has a range of ze r o t o 65, 536 patchesavailable. reduced to 16, 384 m illimi l l i seconds, So me of the controlparametersare secondsi n Mode4. Thevaluedet er m ines s e l f-e xpl anatory, such as ' Level ' ,' V i b the fi naldecayti meof the voice,ie. f r om Sp e e d'and ' V i bD epth'A . gai n,w e come key rel easeto si l ence.l f a loop is act ive a c ro s stheeni gmati c' Mode' w hi ch sw i tch, and one or moresegment sar e r epeat ed is best left until Pages 4 and 5 arc conti nuousl y, the voi ce p lays t he loop drscussed(fhe suspenseis killing rneunti lthe dampi ngti meexp ir es( whent he Ed). 'EXP' is the otherhalf of the comkey i s rel eased),ol herwiset he voice pandingprocessthal was an optionon conti nuesthrough l he rem ainingsegPage 8 discussedlast month. As you ments. S houl d the end segm enl be m a y re member,i t' s a hardw areopti on reachedbeforethe dampinglime expir:s and is very rarelyfitted to the CMI due the voi cestopsabruptl y. to th e non-l i nearsampl i ngdata that The' S l ur'sw i tchi s usefulf or olissando Attacl<and Damping /17'//l V, Ij'a n d p o r t am ent oef f ec ts ,a s i t c a u s e s lChannel cards allocatedto a voice to sustainindefinitelyin a loop that may be ive until a new note is played.New notes are startedat the beginningof the loop withoutplayingany of the preceding segments.'Sustain'determinesthe behaviour of the voice once the key is released.Normally,a voice fades out either playingits loop or until it hits the end of the segments,but when Sustainis on, Damping is ignored and the voice loops for the durationof key depression: upon key release,the voice continuesto play its remaining segments with no decay of amplitude. MUSICIAN OMPUTER [' i'tt i,i-::: r r r l r 'l F r i I r li Figure1. I 'I I n E lllB iFFFn = rl fl TFrL, I : l !:! ::h,:,r ,1!: r 3n.- r ::: t,3n l : l FF D FF :lTFtllI IrI rlRflGsB 4 5 h-E Y U E L iFpfl irFF I I B :T i 'L r r l. :1l ,l TtH , ti I Lrr r :l Ll J F l = = SU ET BIH lH:l!;rlT nnnil ETtCt( r T F : l '1 1 0 e l i l E L L D c | D T 8 l t f l U i II:E T Figure 2. Lrl rl F r:fi TF:L LI]I]F' :TH FIT Lr:i l :rPLl i rl TH t,lI Ir ITE P TH= B I[i H F Il l E = :':1r:i tl TTB tl l ,, = E t !th t: tl l E Ir? r:i Ll !:j ti r{IrB =rl FF FL:LFrTFrj E ftT0:0FF =,_l l _i F,E E Ir r_:U fl ::i T TII'l E = ttl t l l rrl rE =4 E 'l F = r:rFF LE r.rE L : tE \,rrE L FILTE F: = l ! frll I r:rl l 'TFti ,L P FP R tl ET E F:3 r:r:rl l TFtr:rL FILE ' I oonin q r"'b Choosingthe correctloopingpointof a voice wavelorm can make or break a good soundon the Fairlight.Nastyglitches can occur if an inappropriatesamplerate is chosen or if the section to be looped spans a naturalchangeof amplitude. lmagine trying to loop a percussive sound such as a drum. The three loop controlson Page7 providea quickway of findingthe bestloop,and a typicalsetting might be as shown in Figure 3. Here Control 1 is used to define start point of the loop while Control 2 sets the length. Switch 1 freezes the effect of Control 1 and Control 2 when off, preventingaccidental movement of the looping points once these have been decided.A useful featureis that loop parametersare sved with the voice informationas well as any Linked control file, so that the sound is playable even though no performance controls are required. The actual loop points are displayedgraphicallyon Page 4, as shown in Figure 4, where the horizontal axis represents the segment number and therefore time. The loop is indicatedby the row of highlightedboxes under the HarmonicProfilesgraph,and since the voice shown was sampled, there are none of lhese present. This Page offers a convenient method of selectingloopingpoints using the lightpen. 'Start Seg' is a powerful expression control.lt allowsthe startingsegmentof the voice to be chosen accordingto a control value as a new key is played.To explain: suppose we had sampledthe classicsynthesiser filtersweepandplaying the keyboard resulted in a 'fruity' decay. Using a control fader to set the start segmentwould then enableus to play the synth sound from ditferentparts of the filter sweep. As the controlwas movedfrom segment1 to 128,thesound would begin with plentyof filtersizzleat low control values but become shorter and moremellowas we startedthesound further down the sweep (by increasing the Start Segment number).This technique can also be used to control-the amount of 'breath' on sampled wind sounds or the amount of bowing on stringedinstruments. Next month, page 5 and some revelations concerning the mysterious 'Mo d e' . r t.ltt I t-'E , X!IJ2 ;ni i E@m @ p:t,:h* :- i':,r F t,t!i L'l * F 3r 3fi r * tPr P .:r.i nreter [l ,rntr,:I l l Ll trE R anq*, 1, I F:1,:h L I,F r - l l l . L- IF F !, LE (IE L rrl -:'99 | Lt- tt:,J 5 t: . : ht r_F l-: l .: r-ti TF,Lt-r, I' l E \ r,rE L f I I L I LFJ NHNPI TID B TTTi D K E L I S 9 N IIO P gR TIi I'l E N TIJ 8-16:l :13 ON , OFF OT.I, OFF ,]TL L ! 8-l !7 I:IJH S TR N TT I TIE OH , B FF U IB R IITI IIE FTH 8-I?,7 U IB P IITD 9FE E D A -I?7 LI]D P I]ON TR |]L ON , D FF LD D P S Tf,R T LI L00P tElrETH S-128 S T B R TS E D M E N TI - I 2 8 SLUR ON , OFF 9 U 5 T FI N I 0n,0FF D : i c .f c I D c c i UUILL: gTE I' IID I Figure C ON TR OLP R R F}l E TE R S TON TR OL FILE ' H oI'E = 4 E X F,= I]FF LE U E L = K E Y U E L FILIE R =8 D FI'l P Il l G = S E R TTf,C K = IF UOIEEs, LOOP r:Ll ggFti D o P N R TFIIIE N TO S P E E IJ rl D ti S TTl H E CD 5l ,l TcH 3 OFF 3{ OTI Lri 0P C i l rR L = LO|JP S TIi R T = LIJI]P LN .GTH = :JTffR T sE G = U IB IIE P TH = C N TR L3 U I8 S P E E D = S E IIII? 9TFTN IN S S TIC K B B 9S GT C B E LLOB D TR H N INTRL. ::H Tr-HI IT{ TF;L1 D N TR LZ I S LIIR = S l ,l Tr-H a S U 9TFIN = tl FF E I:$T|IIT GR N GS R S I,ITC H . Iti l E ti r:rtl l'1F tt Il S TR tl l Irl q H 0I|E , H FIR tl 0N IC l I \ J i II I I I I \ I L00p l [ l |n PL D T I I tt II \ \ I .1 THE T'AIn'LTGIIT ETKPEATTYED Samplingmay be the CMI'smost talked-aboutfeature,but asthis article shows,definingsoundsusingharmonicinformationcanbe just asdramatic. Izm Grant f ' a\ J o far we have discussed only one method of actuallycreatingsounds with the Fairlight sampling.This aspectof soundformationis probablythe singlemost importantfeatureof theCMl, and was cerlainly the focus of public attention when the machine was announced. Horvever,the abilityto specify sound by means of harmonicinformation can not only resultin someveryinteresting sounds, it's also rather useful in an educationalenvironment. Two display Pages,4 and 5, allow the construction of waveformsby harmonic data. They deal with exactly the same informationbut presentit to the musician in different ways. Firstof all,though,let'sclearup a little mystery that's been evadingus for some months - the Mode switch.Actually,this is very simple and is thereforesomething of an anti-climax.When a voiceoperates in Mode 1, only the first 32 segmentsof waveform RAM (4k bytes) are used to representthe sound.An unloopedMode 1 sound will stop at the 32nd segment, even though another 96 segments of RAM exist. ln order to compensatefor shorter note event time as playedon the keyboard, each of the 32 segments is looped severaltimes beforemovingon to the next segment:this maintainsa fairly constant net event lengthfor any pitch. Mode 4 uses the entirewaveformRAM (all128segmentsof it)and is alwaysused for samplingsince long, high bandwidth soundsneed lots of numbersto represent them. So what's the use of Mode 1? Well, calculatinga time waVeformfrom harmonicdala can be quitetime-consuming, especiallyif the supplieddata is detailed and enablessubtlenuancesof soundto be generated.However,more oftenthat not, only a simple waveformis required, and to calculatetheRAMwaveformfor all 128 segments when a short loop is all that's needed is rather wasteful,to say the least. There's no hard and fast rule aboutwhich Mode a soundshouldbe in: the choice is entirely the musician's. However,usinga voiceas the destinatlon for samplingdalaalwaysresultsin all 128 segmentsbeing ovenvritten,even if the voice selectedis Mode 1. rage ) Figure1 shows a typical Page5 display. This page displaysthe harmonicovertone series as a set of 32 'faders' similarto those on a graphicequaliser.Eachfader is logarithmicin natureand hasa rangeof zero to 255, allowing a good degreeof control over harmonic amplitudesand thus enablingthe applicationof a Fourier type harmonicseries. As an example, Figure 2 shows a squarewave generatedby the CMl,computed from the valuesof Fouriercomponentsshownon the faders.Theresult- X U OIC T' 0 fl rlFH D , HRRNONI C F fiDERS cUK I c N T SEGI'lEN T KL J zL t{ 0 4 56 78 I c0tlPl J E I 1 r 1 t l l 0 r 234s e7 FBue2 h? Frgue 1. N antwaveformis visuallyverysimilarto the realthing,and perhapsmore importantly, soundsi ndi sti ngui shable. However, the powerof the CMI liesin its abilitynot only to compute a complex waveformfrom a set of Fourier componentsso that it can be played on the keyboard,but alsoto computea different wavelormfor each segment. Every segmen\ has a unique Page 5 display,so while a Mode 1 sound has 32 sets of faders,a Mode 4 one will have 1281The currentsegmentnumber is indicatedon thedisplay,and thisallowsa synthesised sound to change drasticallythroughout I I I I 22 ? ? ? ? 2 ? ? 2 3 3 3 890I 23 4 5 6 7 8 9 0 l 2 I S11UBRE 11 ODE' 1 itsduration,simplyby the userfillingeach segmentwith a differentwaveformcalculatedfrom its own Page 5 fader settings. ln fact,the techniqueof usingdifferent waveformsegmentsas the sound progressesis very much the domainof PPG synthesis. Generallyspeaking,theseprogressions are known as wavetables, and in the PPG,a sound consistsof a set of 64 waveformsthat reside initiallyin EPROM(theyare transferredto RAM on power-up)which are read out sequentially when a key is pressed.The idea behind this systemwas to circumventthe need forfiltersby constructingwavetablesthat held a set of reoresentativewaveforms of, say,the classicfiltersweep. Unfodunately,this resultsin a very hard,metallic sound, as the sound changes abruptly from one waveformto another, slightly differentone.lt's stilla good sound,but in the interests of flexibility, PPG have chosen to incorporatethe usual VCFs andADSRsas wellas exiensivewavetable modulatlon. The CMI is also capableof this forrni,l synthesisto a limited degree,using the loop controlson Page 7. For example, supposewe had filled all 128 segments with waveformsthat changeveryslightly as we progress through the waveform (see Figure 3). Now, if the loop controls were set up as shown in Figure4 (thisis a Page 7 display),moving CNTRL1on the music keyboardwould resultin a different timbre when the note was played.Using this techniqueallowsfor some expressive playing,sincethe principleis ratherakin to varyingthe filterfrequencycontrolon a synthesiser, the only difference being that the actual timbres can be radically different from one segment to the next. To increase the timbral movement within a sound, CNTRL2can be patched to 'LOOP LENGTH'on Page 7, resulting in sections of differgntwaveformsbeing read out repeatedly.Since the waveform data is computedby the CMl, it's always constructed so that the waveform fits exactly into one segment, thereby overcoming looping problems. FourierSeries Well,with all this talk of 'Fouriercomponents' and the like, some of you may reasonablybe thinking'what's it got to do with music?' The answer,of course,is not much. Only scientistsand engineers delight in quantifyingthe world which our senses seem to handle perfectly adequately. However, in order to exprbss ourselves explicitly and unambiguously about a wide variety of concepts (someof which may be abstract) we need to use the language of mathematics. Fourier analysisand synthesisare mathematical statementsabout somethingwhich is not intuitivelyobvious: the fact that any truly periodic waveform can be decomposed into an infinitesum of sinewaves,usually called harmonics.Similarly,any periodic waveform can be constructed from the sum of an infinite number of sinewaves. The sinewaves have frequencies that are relatedto the fundamentalof thewaveform in such a way that the second harmonic lies at twice the fundamentalfrequency, the third harmonic lies at three times the fundamental,and so on. The fundamental itself is often referred to as the first harmonic. Of course,obtaininga reasonablerepresentationof a desired waveform does not require an infinite number of sinewaves: more than 16 is enough to give a good approximation.The Fairlightusesa maximum of 32 harmonics,which enables most waveformsto be synthesisedwith a fair degree of accuracy. Figures5 to 8 show the developmentof a squarewave by successivelyadding furtherharmonics and using Page5 to compute the resultant waveform.The squarewave doesn'tcontain any even harmonics (2, 4, 6 and so on) and we can see that the lower harmonic numbers set the basic square shape while the higher ones fill in the bumps and sharpenthe edges.Evenwith all the odd harmonics the Fairlightcan compute, the square wave is still not I visuallyperfect,but it soundsOK. 1984 E&MM DEGEMBER 0 t' tH8 NIt, I,IFIU E F|j P IlN I S P LR Y Ftguo4 S I ,IEEP C O N T R O LP S R R I 'l E T E R S C O N T R O LF I L E . H O D E= EXP = LE U E L = FI L T E R = IILISSFNI0 4 0FF P0RTFHENT0 KEYUEL SPEED 1l tl0NST TIt4E DFH P I N G= l A g f iTT f f C K = 0 UO I I E S , I,IR ut L|]|]P C N TR L LOOP 9TH R T LLl OP LN D TH I |]FF a OFF J U I B D E P T H =& U I B S P E E I ] =g tl K FilNTiiI FI i'i"i"i Itl il IT T I ,l CLb I CN TR L T S L U R = 0 FF S U g T F I N = 0 FF 1:-t45 Flgnr,o5. I ON C}ITR L l Fgtre8. MUSICIAN O MPUTER TIIE T'ATRLTGIIT E)KP&ATNED Waveforms,lightpensand interpolationall come under examinationin this instalment of our FairlightCMI GrandTour.Ji* Grant ust when you thought it was safe to open up a copy of E&MM without reading anything about the world's most influential comoutermusicalinstrument, your intrepidreporterreturnsfrom a New Yearhangoverwith anotheractionpackedepisode.This month we look at the informationpresentedby Page5 in a slightlydifferentlight. You'll remember that Page 5 held the values lor 32 harmonicfadersand computedthe resultant waveform for the current segment. You shouldrecallalsothatthe onlywayto createa completesoundof 32 segments was to define the fader levels for each segment and compute over the whole waveform; or define a few segments and Fill the harmonicdata to the rest of the segmentsbeforecomputing.lt's not hard to see that this method of creating soundsmay be very precisebut can also be extremelytedious.In a lot of cases,all we needis a wayof tailoringthe harmonics as the sound progresses: harmonic envelopes,in other words. EnterPage4. Figure1 is a typicalPage4 display,and shows that it's one of the two Fairlight display Pagesto be almost exclusively lightpen-driven. The largedark areais in fact a reversevideoimage,and pointing the lightpenin this regionresultsin an arrowcursorappearingon the screenat the currentlightpenposition.For those unfamiliarwith the term, the lightpenis now a fairlycommoncomputeradd-on, mainlybecauseof its simplicityof operation.Containedwithineverylightpenis a fast photoelectricdiode or transistor whichproducesa voltagepulseas theW linepassesbeneathit. Usually,the pulse is squaredup and passedto the video controllerchip, which storesthe W line numberand positionalong the line in a coupleof registers. This informationcan then be used by the programmer to initiatepredefinedevenlssuch as plotting a point or executinga command. The Fairlight system is no different, except that the video controlleris constructed from discretelogic chips and resides on a single eight-inch board withinthe CPU.In additionto latchingthe TV co-ordinateswhen the lightpen is used, it generatesan interruptto the processorsto executethe selectedtask. At firstglance,the graphareain Figure 1 l o o ksa bit c onf us ing b u t i t' sre a l l yq u i te straightforward: the verticalaxis representsamplitude whilethehorizontal shows time and hence the seqment number. Along the bottom of the displayare the harmonic numbers 1 to 32. A small triangleunderthe numberindicatesthat the time profileof that harmonicis being displayedon the graph, while a cross shows that the proflle has a non-zero vatue. So what does all this mean? Have a look at Figure2. Two profilesare shown, one of which is the Firstharmonic(leftto rightdownwards)and the otherthe Third (left to right upwards). On receipt of a Computecommand,the CMI will fill the waveformsegmentswith sound which initiallyat least,hasa strongfundamental NIIEi; rl tl |1ri ll tl H fi Fi I'ION I H FR 145 l ' l rl l rE , ROFILES mrlfl r lllr lllttl l!i45r I [!:i tr I.L EHF, [IILE TE I FLr:rT ! 2:rrJ :j l ! :tE t1c " t1 n tr FF' i tF t- t I llIr Ei: r: r:r11f1H fl Il I-I11Eff | r :r l r :E, I ::; HBFII,1 f l n l E' I H Fi F]11[iI HI: FF]i IF I LE i L r:rr:rF Irirfll FLrrT .!i:i:ji:i i tsj rl it! tr l: f1 li'fti M A R C H1 9 8 5 E&M M 't I l. :)ut degenerates into dominant third rarmonlc. l[r f1l' 1Hf1Il triF : r l : It l l i rrE FI:'F l 1 IrI :FL H , t 1 1! _ . _ r {r , _ l : j _ : , t _ ! E B _ . _ _ : T E F c : [| . ,.lankprofilegraph. i"lore About Mode One of the previously mentioned featuresof a Mode 1 voice is the way in which the first 32 segmentsare looped several times to maintain the net event timeof the soundacrossthe keyboard.In fact, we havesome controlover how long a segmentlasts beforeeverythingmoves on to the next one, and this is accomplished vrathe profile. Figure4 shows a harmonicprofilegraph with the duration profile indicated by a double line: the defaultvalueis approximately50mSper segment and increasesas the profile is drawn higherup the graph.This is particularly useful for creating sounds with a short click at the beginningof each note, suchas that of a Hammondorgan.Avery shortdurationvaluecan be drawnfor the first one or two segments, and then a longer profile for the remainderof the sound. lf the duration profile is made zero,the sound degeneratesto a Mode 4 condition,except that it only lastsfor 32 segments. Another interestingaspect of Mode 1 sounds is their ENG profile.This is an artificialenvelopethat's superimposed on the waveform in much the same waY as the more usual ADSR principle.But this one's a lot more flexible.When the Compute command is given, the CMI calculates the waVeform segment by segment and scales the amplitudeso that it fits exactlyinto the dynamicrange of eight bits. The ENG profile is also generated(and its shape implied)by the harmonicdata, but can be alteredby the lightpen to control the amplitude of the sound on playbacltr Auxrlary Functrons A''I'F Along the very bottom of the display Page are a number of usefulcommands. Clear deletes all the displayed profiles from the graph, but they remain active and can be broughtbackto lifesimplyby the programmerselectingthe harmonic numberswith the lightpen.Delete,on the other hand,merelyremovesthe currentlyselectedprofile.Thesamesoft of structure appfies to Reset and Zero. Invoking E&MM MARCH1985 l l l _ r I l-: l l F Frl .' : l'1[r Ir I H i rF;l l i rl lI r-: P F:rtFI LE g EE * , . l *u el45 mfnl LU I:IP ' --t " ; I tl t :'a :' C I::L EF F , IIE LE TE F.E '1E T r li ;l F i Ii l 'IFr:i Resetcausesa confirmationmessageto be printed and also results in Page 4 being restored to a complete default condition.Zeroisn'tquiteso drastic,and resultsonlyin the currentprofilebeingset to zero. Everytime you give a Compute command, a new energy profile is generated.Scale is the opposite: it redrawstheharmonicprofilesfrom a modified energyprofile.This is not without its dangers, however, as it can result in some harmonic profiles being scaled beyondtheirmaximumamplitude,which leadsto clipping.The Fairlightw7linform you of the situation when it occurs (by displaying'Overflow')but is powerlessto preventit happeningif theScalecommand is issued. The only way to recover the soundthen is to reloadthe voice. Timenow to introduceanotherconceot with which some of you may not be overly familiar.lnterpolationis the skillof guessing an unknownvaluethat lies between two knownones,and is commonlyused to predictvaluesof pointson graphsthat aren't the actual ones originallyplotted. When the Interp switch is On, each waveformsegment is computed from a mix betweenthe harmonicnrofilesof that segmentand those of the next one. The differencebetweenthe two is subtle,and is only reallynoticeablewhen the profiles .-,-.t.-,.-. lrii rr:l E r I i ili F I r:i JtlFU TE rL,: j ':r-tl LE o It1 TE F:F r-' . E f,ti contain rapid changes throughout the durationof the sound. Incidentally, becoming proficient at usingthe lightpenfor drawingcan take a lot of practice,so the CMI helps out by providinga Join Plotselector:when Join is active, any two points struck on the graph are immediately connected by a straight line, while fine detail can be drawn by selecting Plot. I imagine that most of you will be familiar with the Fairlight'sLoop function by now, so I won't go throughit all again.Sufficeto saythenthat Page4 offersa quick way ol drawingthe loop startand length.Mode 1 soundsare alwayscalculatedso that the waveform fits perfectly into a segment: the first harmonic does one cycle, the second harmonictwo cycles, and so onGone are the Bad Old Days of trying to sample a sound to make it fit segments evenly.All you haveto do now is use any old loop to span the sectionsof a wave' formthat are of interest,and Bob Moog's your uncle. Next month (yes, there's still more to come),we'll take a look at Page6 which, arnongmany other weird and wonderful things,allowsyou to splicea sounddown to no more than 16,384thof its length. Ahd you thought a razor blade was r powerful. .. TIIET'AIRLTGIIT E)KPEATTUED asPage5, you can When a CMI pageisashelpfula sourceof musicgraphics bet your lifeit needsa lot of explaining-sothismonth'sepisodeis dedicated entirelyto it.J i,nt()ru,rtt I f you're tryingto createa new sound I on the Fairlight,whether it's from I existingsampleddatausingPage8 or harmonicprofilesgeneratedon Pages4 and 5, you can be surethat Page6 willbe referredto over and over again. At its simplestlevel,Page6 is a siatic 'oscilloscope'containingone segmentof the waveform RAM. Like Page 4, the largeblack areais a reversevideoimage and representsthe region that can be hit by the now-infamouslightpen.But unlike an oscilloscope,which acts only like a window on the information,Page 6, in conjunctionwith its commandsandlightpen, behaves more like a door through which we can directlyaccessthe waveform data. The ManualApproach Regularreadersof this serieswill probably recallthat each segmentconsists of 128 bytes,and that eachbytecanhold a rangeof valuesfrom -128to 127,giving a grand total of 256 possiblevalues.Now, we can highlightany particularbyte by positioninga narrowverticalwindowover the display area. The byte in question, shown in Figure1, has its positionindica te d b y P 0I NT an d i ts v a l u e b y L EV E L: thesecan be changedby typing in differentvaluesfrom the alphanumeric keyboard.So, theoreticallyat least,you could type in 128 levels for each byte shown in Page6, and repeatthe process for all 128 Page 6 displaysto coverthe entiresound,giving16,384levelsin all.In practicethough,such a feat would take an unbelievable amountof manuallabour (exactly what much of the Fairlight's software was designedto eliminate)to achieve,and this has led me to wonder whether this feature will be dropped when the Series lll Fairlight,complete with waveform RAM of megabytedimensions, makes its appearancelater this year. A more practical approach is, of course,to make use of the lightpen.This is as simpleas drawingon the back of a bus ticket, but just in case even that is the beyondthe user'sartisticcapabilities, J 0 I N and P L0T f unc t i o n sa l s op re s e n t on Page4 are availablehere,too,to help out with the drawing of geometric snapes. In fact, trying out a few samplesketches soon revealsthat waveformswhich look drasticallydifferentmay sound surprisinglysimilar.Scientificallyspeaking, this is probablydue to the fact that as a lrir T r- C I il[ r t t , , : r:rl'1ll H ll Il tl l t H | | E F r:rF11 IrF:B !i I ttrj : : ' TEF F:B T E , iTBF i T r jlr _r F Figure1, 5lr E * f llntllEfliJilIl I::FiBFH r::E[i t{ [ f{ T !:::: i .-rr, r, Er, t tillf,G[m IiIEf,I[E';,'11i1n -3;1';{ :-t:F'p i r' -r il i !F 1 :? FIEf,ffiEIID r n j r ] F f '- 1 r n i 1, :i,l i t i ': : t i ': r r [IftMEm f 'rr rr nri r:ii I i i 3t i,:'r-l r.I.3L.'e I?fjltrro{E[ fiirilUfiflfifi :-rri tf h Effil] ,: ,:,n,n,3r;il L-: i ft,Iir.-rr'il m[film nt[ilImfiffil'., ilrt t,:,r Ll .J Pl 'r * r 3tl ,:,r l ,: ,:,ri rlr3i'ril lililI] tifffn ': ,:,ri I' 3n il ,: i, r,rL,3r, '|:l tlf{iliti IIIIH i ii tritr 3r-ril ti':ti,:l mlffi[i ':,:,rir nEfitrFEm ,: i,L,r,i3tril R!roI{#Tl i,-l r,ri, i r-,il Iff,illEnnB ,:i, r,,n-Jritl i,r',:] lifiE : ':,r,ir,, rilitti,-1 r, t[illfl I r''| :-tl'r'rin+r'i : rr,:l l![AlffilfffE I r f : : : : , , r, rt l ', L I r . H T i I i i , r r - T 'i F E r ,r h':t'E [[IG 'rr T i F E l 'l ri R Itl tr l ul' lNr if lIl r:ii r U fl Ir i ti l 'IFLIN C : : ; H I 'l P L ER I i T E F I LTEFI LUI,I FI L T E E H I L i H t r - r H F 'F r E g S u R I 4E j i j B I .1 r:rFF 5 F I 'I F . L EL E U E L T F I I T : G E EL E I , I E L T RI I I ] E R I I E L H T t5E t5 u 1,1! iHt'1 F L t TI I: l F L H \ . A P R I L1 9 8 5 E&M M species,we have little prior experience gainedfrom our sensesthat relatesvisual ti me dom ain wav ef o rm sto w h a t w e perceivein terms of harmonicsor parti a l s. But Page 6 waveform-drawingis of enormoushelp,firstbecauseit givesthe user extensive and direct control ol waveform RAM with one sweep of the hand, and second becausethe abilityto bringabout such drasticsonrcchangeso simply and visually(almost artistically, some might say) is a practicalitylight years away from the sophistication and complexity of the underlyingmachine and its software.Or to put it anotherway, it makesthe CMI seemlessof a beastand more of a pet. OMP U T EM RU S IC IA N i rt : I t : f I i ' 1 8 F, I 1 1 I B Ifiii - ' ' r lllr ilr i : i i I'FL I FH IL FIt.IIi Lr:rt] I-ILItF'H II.H ' r-ri JFF[:':11F _ fl 1.1i : 'J F] : . H I ] F 'L ELE I,IE L T F : l r . r : I F , LE IIE L T F 'I I : i L , E FII' E LB I :59 r5 I l'1':, r_rF i- tr I t It]:FIti ,' F ig u r e4 . The Practical Approach Alterationof the display imageis not reflectedin the waveformRAM untilthe F I L L commandis used.Thisallowsthe reverse video field to be used as a scratchpad area in which waveshapes can be developed before they are finally committedto RAM. Lookingagainat Figure1, noticethere are two 'slider'controlssimilarto those on Page 5. These control the segment numberto be displayedand the stepping ratethroughthe entirememoryinstigated when the command Step is issued.Also shown are three classic waveformstriangle,sawtooth,and square- which deposit a perfectly fitting single cycle wave into the segment.The pulsewidth of the square can be varied from 17oto 99% by changingthe valueheld next to the squarewave symbol. AuxiliaryCommands In additionto the graphiccapabilities of Page6, thereare a numberof commands that can only be entered from the Fairlight's alphanumerickeyboard.Figure2 shows the range of functionsavailable, as presentedby the H E LP sheetmenu. First off are a f6w utility-typecommands.GA I N scalesthe displayeddata by a specifiedpercentage:if the rescaled waveformis about to exceedthe amplitude rangeof the system,the CMI willask you whetheror not you want to proceed and therebyinduceclipping.lf you reply in the affirmative,the command will be d u l yex ec ut ed.M ean w h i l eth , e I N VE R T commandinvertsthe phaseof the waveform:this is usefulas a preludeto someof th e o t her f unc t ion s s u c h a s M IX, MER G Eand A DD. A parlicularlyneat little corirmandis ZERO ,whic h allowsu s to c re a tea n u l l voice in preparationfor the A DD command. The entire waveform RAM can be ' AH IGE T T ING A B IT OVERDRAW N' A T T H E B A N K , T IME To Co/YlPoSE AN oTTHHEERR ME CA GA -S M ASH Ht7 A{o SIN6 L E . I T H INK .' I lJ I r t f l u lr l' lF fltl r:ir:rl_llj Ir ::iHl\lF,L l il [ :i H IIP LE E FITE F I LTE F Lr_ri l FILTE R H IIJH r : Lrl 'l FFi E i trJR I qi l :l U H i I iJ r-l FF i B I {P L E L E I . I E L T F t l r : r : ; E FL E r . r E L T EI i r : ; E F : t r E L h i ' i 55 t5 E i lil'lP L E II IS FLItY Figure 5. tu rn e de nd on end by usi ng RE V ER SE , and this resultsin the backwardssounds that have become familiarto pop music followersthe world over. R E F L E C T i s a l ess commonl y-used but if anythingmore interestingvariation on this theme. lt allows us to olace an imaginarymirror in the sound and reflect everypart of the waveformin front of this mirrorto waveformRAMbehindit. Takea look at Figures3 and 4 for before and afterviews:the 'mirror'is at segment64. Now on to anotherof the seemingly insurmountable problemsbroughton by the onset of new musical technology. Very often, when a sound has been sampled,the beginningof the captured data does not occur at exactlythe startof the RAM, perhapsdue to some extraneousnoisepretriggering theADC.However, if the effect isn't too severe, a convenientmethod of correctionis to R0 T A T E the soundwithinthe waveform RAMto bringthe startin linewith byte 1. This has the (oftendesirable)side-effect of shiftingthe first part of RAM to the end. SeeFigures5 and 3 for anotherrevealinq beforeand after H^{ M/I/1I!A, ..JHINK I'LL ST AR T WITH A + ,' + RHY T H M ,.. l i magi ne N 0IS E w i l l b e f air ly self to eventhe leastclued-upof explanatory this column'sreaders:it fills sectionsof the RAM with the output of a random numbergeneratorhiddeninsidethe sottw are. Funni l y enough, t he GA I N command is also used to tailor the amplitudeof the noiseto that of the rest of the sound... N ow , B LE N D i s a str angelyout of place command. Personally,I think it shouldbe on Page4, since its role is to help smooth out glitches caused by imperfectloopingpoints.lt may be thatto finda good loopit makesextensiveuseof extrapolationtechniques,and that seeing as this is a centralfeatureof the MI X and ME R GEcommands,Fair lightdecided to bungit on Page6 alongsidethem. However,ratherthan discuss the remainingPage6 commandsin any detail rightnow, I thinkit's probablybest for all concernedif I demonstratetheirpowerin the context of a typical edit session in whicha soundis createdfromscratch,ie. withoutany sampleddata. So, now you know what l'll be talkinq about next month. 5Ai IN U T ES LAT ER ...AN OfH ER A AST ER P I E CE F IN ISH ED J T H IN K I'LL J U S T D O .F ouR R EA^IXESO F T n t S O N E J , 1 S /r{EA HEAD: JUST TR/ING TERL''TE E & MM CHI APRIL19 85 I' l l THEE'ATRLIGIIT E)KPEATTUED In which we takea lookat the differencebetweenlinearandlogarithmic andincidentally conversion, endupcreating asoundusingthe Fairlight's synthesis faciIiti es.J im Grant inthemodern ostpeopleinvolved musicindustryarealready aware potenincredible of theFairlight's tial as a music prodrction tool. These days, you switch on the television,radio or record player in the almost certain knowledge that a CMI will make its presencefelt somewherealongthe line, and when you considerjust how usefulits specificationis to studio Ongineersand producers,that's hardlysurprising. Even in 1985, there aren't many machines capable of spreading six octaves of sampledsound acyossthe keyboard,and manipulating that sound within user sequencesto the nth degreeof preciSion. But if you're fortunateenoughto sit in front of a CMI for any length of time without any production deadlines to meet, you'll soon discoverthat its creative power lies as much with sound synthesisas it does with musicproduction per se. Pages 4 and 5 are good examples of this in that they offer the fairly standard synthesis tools of harmonic sliders and profiles,but Page 6, which we introduced last month, is something of a softwareoddity,since it allowscontrol overthe wholewaveformfrom a single byte to macro type comma n d s s uc h as G A IN , Ii 1IX a n d IIER G E . Now, for any command or processto be really useful in the field of sound synthesis, it must be responsiblefor some radicalchangein the soundstructure that's both intuitive and easily understandable. Forexample,theVCFof an analoguesynth changesthe sounda great deal, and can be simplyexplained and understood in terms of the attenuation of harmonics.FM synthesis,on the other hand, also resultsin vast timbral differences, but comprehensionof the processes involved (and their possible results)is a lot more difficult.That'swhy actuallyarrivingat a pre-specifiedsound on sonrethinglikea YamahaDX7requires so much in the way of practiceand patience - and why so many musicians prefer programming analoguesynths, evenif the ultimatesonicpotentialisn't as great. Fortunately, the Fairlight'sinternal configurationside-stepsmost of these operational problems, and a good example of how this is done is the A DD command. This takes a choiceof segments from one loadedvoiceand adds IIRUTFORN D I SPLSY nautFoR nD IspLny 0i t18tl D , f.BU tF oR n D Is ptBy them directlyinto the samesegmentsof the currentlyselectedvoice, scalingthe amplitudeto avoid clippingif necessary. lf you were to A DD all the segmentsinto another, playing the keyboard would result in both soundd being heard togetherbut only usingone voice.Figure 1 shows a square wave and Figure2 a R D D C O Il noD E, 4 l l oD E' 4 BD D C 0n l l oD E' 4 sinewaveboth residentin differentchannel s of the C MI: the resul t of ADDing them togetheris shown in Figure3. The addition's proportion can be varied by using the GA I N command prior to the acti on,or by repeatedl yADDing one voiceto anotherto increaseits amplitude relativeto the comDositesound. OMPUTER MUSICIAN onr Ai l D , fl I xcon mtn tmum MSB=1 1111 VoiceWhveform (Triongle) FilD, SYNT0f4 Sl ]U N D SR N PLIN G S8I1PIE R R T E F ILT ER to'l F ILT ER H IG H C O I1PR ESSO R I 4O8O H Z I 8 OF F SAi l PLE LEU EL T R IG C ER LEU EL T R IC G ER IEL8Y 255 15 O NS Figure 4. Linear conversion. SSIl PLE D ISPLR Y 0111 Figure 8. S Y i l To r' l 0t1l 1R N D , SO U N DSBIl PLI N G SR IIPLE R ST E F I LT ER LO II F ILT ER H IG H C OI1PR ESSO R I4O 8A H Z 1 8 OF F SBI1PLELEU EL T RI G G ER LEU EL T R IG G ER D ELR Y 255 IS 9 NS SR Il PLE D I SPLfi Y Figure 5. Non-linear (logarithmic) convercion. Figure 9. VUIUL: 11txc0t! FE R G C O I ' 1 noDE, 4 l" Linearity Now seems as good a time as any to explain sornething we've mentioned many times in the past but haven'treally discussed in any detail, namely the differencebetween linearand non-linear voice data. As you'may remember, a E&MM MAY 1985 waveform is stored in 16K of RAM, in which each byte has a binary value that c\oresponds directly to the amplitude of the waveform at that point. A byte consistsof eight bits, and consideringall the possible combinations of these results in the amplitudeof the sound at any point being limitedto one of 256 levels. The term 'linear'refersto the relationship between the actual amplitude and the value of the binary number used to representit. lf all this sounds a bit on the technicalside (and it ought to), have a quick glanceat Figure4. This shows that zero amplitudecorrespondsto binary 0, while maximum negatiVe excursion' is 85 IIRN! PFtl I.IBUEFORI,I DISPLf,Y il O D E, 4 T EST I'l ol E ' 4 l l i fl N D , l r f,uEF oR r l D Is PLBY X l 1 l 4 8 N D, r f,uEFoRi DISPLBY |-\ re p re s ent edby 1111 1 1 1 1 ,o r 2 5 5 ,a n d the maximum positive value is held as Well, 0 1 1 1 1111,or 127.S t i l lc o n fu s e d ? the valueof the Most SignificantBit holds the key. lf that valueis 0, the waveformis positive,while a 1 gives negativeexcursions. Anything else in between is in simpleproportion.Thisform of representation results in a ratio between the smallest and largest signal that can be handled (or in other words, dynamic range) of about 48d8. You might consider that to be not a particularlyimpressive figure, since it means that at low signalamplitudes,the sound is moreor less surroundedby hiss. The fact is, storage (in one form or another) of low-amplitude sounds is a perennialengineeringproblem,to which the most common solution is some sort of noisereductionsystemsuch as Dolby. In the digitalworld,and as a directresult of research into digital telephony,a ditferentsolutionis to use more binary bits of the byte to representlow-signal levelsthan you use for the highones.This is shown in Figure5, in which the lower valuesof the trianglewaveuseup moreof the binary bits than a corresponding increaseat largetriangleamplitudes. The binarydata is now no longerlinear- it's logarithmic.For the waveform to be recovered, the data must be passed through a DAC that has a curve bent the opposite way to 'straightenout' the sound.I know all thissoundsmorethana littleinvolved,but it doesbringthe magic dynamic range ratio up to about 72d8, which is at leastrespectable. Onlycatch is, the processonly achievesthis with a correspondingincreaseof quantisation noiseat largersignallevels,thoughthisis maskedby the volumeof the signalitself. You might be familiarwith thisconverB6 IIII;T tl AN D . sion process under its commonly used name of companding,and it's a system used by many hardwaremanufacturers includingLinn and E-mu. So if it's so good, why doesn'tthe CMI use it? Simple. Rememberyour school days when you added log numbers to multiply?Well,thisis whatwouldhappen i f th e e AD D command w as used w i th sounds held in the form generated by Figure 5: instead of adding the sounds togetherto producea mix, we'd get the product, and end up with VCA-type effects at low frequenciesand strange sidebandsat higherones.Whichisn't,all things considered,a particularlydesirable state of affairs. l.a' l -l l x l n g Anyway, enough of the lecture and The MI X command backto the Fairlight. can also drasticallyalter the waveform it generatesa crossRAM. Essentially, fade between two specified segments which must not be adjacent, ie. there must be at leastone segmentin between. The waveformmemoryof each segment between the stad and end points contains a proportionof the existingwaveform in that segmentand that of the end segment: this is best illustrated by examiningFigure 6 and Figure 7 for before and after views. Rememberthat the new contents of each segment is a mix between where you are in the waveformand the destinationsegment. Thus from Segment 2 onwards, the waveform simply fades up to a square wave. MI X is most commonlyused to add a clean fadeout to a sound that decays to noise or doesn't decay properly in 128 segments. Have a look at the percussionsound r ,l nuEF oR r ,iD Is PLBY TE S T noDE' 4 UUILL. I TE S TI l ' l o D E' 4 sampled using Page 8 and shown in Figure8. lt's pretty clear that the sample ends in a dither of noise. Now, suppose we needed nothing more than a short percussive strike, and that only the beginning of the sound was of any interestto us. A quick solution would be to turn to P age 6 and ZERO , say, Segments64 to 128, halve the sound, and then MI X from Segment 45 to 64. Lookingat Figure9 shows the result- a sound that dies away evenly to a noisefree end, much to the relief of all concerned. l .l E R GEi s fai rl ysi mi l arto M I X - wit h one fundamentaldifference.Again, a form of crossfadeis generated between startand end segments,but this time, the previous contents of intermediatesegments don't figure in the result. Quite simply,the segmentsin betweencontain a decreasing proportion of the start segmentand an increasingproporlionof the end segment.Figures6 and 10 (oh yes, very logical- Edl revealall. The MI X and ME R GE commands ar e t r em endously powerful for splicing together soundsof differingoriginsand producing an even fade from, say, a violin bow attack to a sung 'ahh'. Creating a Sound So, now that we've discussedmost of the commands available, let's try to create a sound using everythingexcept the Fairlight'sPage 8 samplingfacility. Thequestionis: am I allowedto use Page 2 and pulla soundoff-diskto work with? Well.I've decidedl'll have to cheat a bit because I already have a thoroughly marvelloussoundcalled PAN.VC.which attacks with the characteristic breath chiff of pan-pipes. MAY 198s I E&MM O M PU T ER MU SIC IAN First off, First off , we configure Page 3 to generate two voices, one with an NP H0NY of 7 in RegisterA to be played on the keyboard,the other monophonic in Register B as a scratchpadvoice. Using Page 2, we load RegisterB with PAN.VC,which can be sbenin Figure11. The breath chiff is clearlyvisibleat the beginning of the sound, but unfortunately,the samplingstadeda fractiontoo soon, and the waveform has a few initial segmentsof low-levelrubbish- nothing to do with Electronic Soundmaker, you understand. The cure is to rotate the voice left to bring the start of the sound proper coincident with the start of the RAM. The next step is to flick to Voice 1 in R e g i sterA and Z E RO it. U s i n g a n e w c o mma n d, T RA NS F E R , th e fi rs t fe w segmentsfrom PAN.VCcan be copiedto the blank voice currentlyselected.Stabbing the keyboardat this luncturereveals that all is well,so the nextthingto do is to work on the body of the sound itself. Beforeany soundcan reallymakethe gradeas far as aesthetics areconcerned, it must have plenty of timbral and amplitudemovementwithin it. A good way of producing harmonically-rich waveformsis to use Page5 and createa few segmentsspreadacrossthose unused by the chiff. Figure 12 gives the general idea - note that the created waveforms are all ditferent. So what about the segmentsin between?Well, th i s i s w h ere ME R GEcomes i n handy, fi l l i n g i n the ZE R Oed segments,and usingthe segmentscreatedon Page5 as the start and end points. OK, so far it sounds quite interesting timbrally(and looks it too, as Figure13 shows) but it's still in need of some amplitude variation. An easy way to achieve this is to invert a couple of segments(numbers32 and 96, say)and l.lI X from segments1 to 32, 64 to 32, 64 to 96 and 128 to 96, using Page6. lf you t've tusr aou6l{T THts NErrrr \ IT CONTAINS ALLOF THE TECHNIQUES 'meon-Ruro-col PoSER'-SoFTWARE ANO STYLES OF IHEWONLDs GREAT. COST T5OOI ONLY EST COMPOSERS!.?ANTUi}| THE 'I\E /l osr BoRDtGAxD,r{tDtocRr solt6. t cnstp Er r ADL ,flo.l$""r!L.os1 look closelyat the differencesbetween Fi gures13 and 14, you shou ldn'thave muchdifficultyidentifying the variationin ampl i tude, especi al liyn the so und'sf ir st quaner. All that remainsis to inserlloop points on Page 7 or Page 4, and adjust the I attackanddampingon Page7. ilow I CANCOI PoSE LIK! A{oZABT AltD BEEtHoylr frL Dl lll6^-f^/{out IN NO TI'',IE! lETs SEE WKAT THE PRO6RAM DOESWITH TITATPIECE oF nAtBlENT rraUSlCt DtD IAST rltoHT.t i+/.€oD