Inthistutorial,we’regoingtocreatea
chromaticpercussionpatchofthe
sortforwhichFMsynthesisisknown.
Startingwitha blankslate,wegotoour
AudioComponentsandopenthe
Oscillatorcategory.Fromthere,wegoto
theAliasFreesubcategory,wherewe’ll
findtheBasicWaveformscomponent
anddragit intoourpatchwindow.1
ClassicFMsynthesisusesonlysine
wavesasitsrawmaterial,sogotothe
Oscillatoreditorwindowdownbelowand
findtheWaveformknob.Turnthisfully
clockwise,sothatit readsSin. Thedisplay
indicatesthatwe’renowgeneratinga sine
wave.It’saboutasexcitingasyou’dexpect- ie,notatall...
2
Wecan,however, turn this basic
waveforminto something far more
interestingbymodulating its frequency
withanothersine wave. Doing so will
createinteresting harmonics not present
ineitheroftheoriginal waves. One way to
dothisinFathom CM is simply to click the
AMFMbuttonat the lower left.3
Wenowhavea newwindowdevoted
tomodulation.Activatethis
modulationbymovingtheSynthesis
slidertotheright-mostpositionforFM
synthesis(theleft-mostpositionactivates
AM,oramplitudemodulation).Thishasan
immediateeffectonthetimbre,producing
a reediertone.Thedisplayaboverevealsa
moreharmonicallycomplexsound.4
That’sstillnotterriblyinteresting.
However,if youplayandholda note
whilespinningthroughtheAmountknob,
you’llhearsomeofthepotentialonoffer.
Let’sclickthecentreoftheAmountknob
toselectit asa modulationtarget,and
thenclickAddMod, afterwhichwe’ll
assignanADSRenvelopeasits
modulationsource.5
Nowthatwe’ve assigned our ADSR to
FMAmount, we use the tiny knob on
therightedgefor the ADSR component to
increasetheamount of modulation in play
toaround0.64 or so. Since we’re making a
percussivesound, we’ll reduce the Attack
andSustaintime to 0 , and dramatically
decreasetheDecay time.6
Thatsoundsprettyneat,butit’smore
likea calliopethana percussivetone–
that’sbecauseouramplitudeenvelope
isn’tverypercussive.Let’sclickbackover
toourSignalFlow,andselecttheBasic
Waveformsoscillatorforediting.Weclick
theOscillatorbuttoninthelowerleft,
thenturntheVolumeknobfullydown.7
Next,we’llclickthecentreofthe
Volumeknobtoselectit asa
modulationtarget,andassignanother
ADSRtocontrolitslevel.Wecrankthe
amountofmodulationtomax,reducethe
AttackandSustainto 0 , andsetthe
decaysothatit ringsouta littlelonger
thanthatofourfirstADSR.8
Let’sclickthe centre of the first ADSR’s
amountknob and assign a Key
Velocitymodulator to it. We can now fine-
tuneboththeoriginal amount and that of
ourVelocitymodulator until we have a
dynamic,woody tone. Back in our
Oscillator,wereduce the Pitch Octave to
-1.000fora lower pitch.9
Stepbystep 2.FMSynthesiswithFathomCM
64 / COMPUTER MUSIC / July 2019
make music now / digital modular synthesis with fathom cm