Physical modeling with

80 Pages·2014·4.1 MB·English

Physical modeling with
A granular guidebook to a new world of sound by
Madrona Labs
ismanualisreleasedundertheCreativeCommonsAttribution3.0
UnportedLicense.Youmaycopy,distribute,transmitandadaptit,
foranypurpose,providedyouincludethefollowingattribution:
KaivoandtheKaivomanualbyMadronaLabs.
http://madronalabs.com.
Version1.0,March2014. WrittenbyGeorgeCochraneandRandy
Jones.
IllustratedbyDavidChandler.
TypesetinAdobeMinionusingtheTEXdocumentprocessingsystem.
Any trademarks mentioned are the sole property of their respective
owners. Such mention does not imply any endorsement of or asso-
ciationwithMadronaLabs.
Introduction
“efutureevolutionofvirtualdevicesislessconstrainedthanthat
ofrealdevices.”
–JuliusO.Smith
Kaivoisasowareinstrumentcombiningtwopowerfulsynthesis
techniques(physicalmodelingandgranularsynthesis)inaneasy-to-
usesemi-modularpackage. It’slaidoutabitlikeanacousticinstru- Formoreinformationonthetheory
ment;theGRANULATORmoduleactsliketheplayer’stouch,exciting behindKaivo,seeChapter1,“Physi-who?
Granu-what?”
oneormoretunedobjects(here,theRESONATORmodule,basedon
physical models of resonant objects) that come together in a central
resonatingbody(theBODYmodule,alsophysics-based).
isallowsforanatural(oruncanny)senseofspace, pleasingin-
teractionsbetweenvoices,andatonofexpressivepotential—alltraits
in short supply in digital synthesis. e acoustic comparison begins
to pale when you realize that your “touch” is really a granular sam-
pleplayerwithscadsofoptions,andthatthephysicalpropertiesofthe
resonatingmodulesarewidelyvariable,andinrealtime.
Alltogether,thisarrangementgivesyouroomtocreateandmanip-
ulatesoundwithconsiderablefreedom,whilemaintainingapleasing
senseofphysicalplausibility.rowinsomefreshnewmodulatorsand
adashofpatchingmagic,andwell... We’reexcited. Wesincerelyhope
thatKaivoexcitesyou,too.
AQuickOverview
Kaivo’sinterfacehasfourmainsections,fromtoptobottom:
• e header section, where the title of the plug-in sits, next to the
patchmenuandsomeUIbehaviorsettings.
• eshapessection, wherecontroldata(andmore)flowsfromthe
KEY,SEQUENCER,LFO2D,NOISE,andENVELOPEmodules.
• epatchersection,whereconnectionsbetweenmodulesaremade.
• eaudiosection,wheresoundiscreatedandprocessed.
ReadTheFabulousManual
If you’re new to all this, this manual is a great place to start. If you
arefamiliarwithmodularsynthesis,orhaveusedKaivo’seldersibling
Aalto,feelfreetodiveinandhavefun. However,Kaivohasnewsome
kindsofmoduleswecansafelysayyou’veneverseenbefore.
ismanualissplitintofoursections:
• Physi-who? Granu-what? –Abitofbackgroundonthetechthat
Forafullrundownonthese,turnto
makesKaivotick. Chapter3,“Kaivo:ModulebyModule.”
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• GettingtoKnowKaivo–InfoonhowKaivofitsintoyoursystem,
andhowtousethevariousdialsanddoodadsthatyou’llfind.
• Kaivo:ModulebyModule–Ahands-onrompthroughthedifferent
partsofKaivo,modulebymodule.
• Patching for Fun and Profit – A starter course in putting Kaivo’s
modulestogethertogetmusicalresults. Tipsandtricks.
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1 Physi-who? Granu-what?
ischapterisabriefprimeronphysicalmodeling, granularsynthesis, Foramoredetailedlookatphysical
andthebasicsofsignalsandsound. modelingandgranularsynthesiswith
Kaivo,seetheRESONATOR,BODY,and
GRANULATORsectionsofChapter3,
Kaivo:ModulebyModule.
WhatisPhysicalModeling?
It’s a digital signal processing (DSP) technique that lets you process
andgeneratesignalsaccordingtomathematicalmodelsofreal-world
physics. Pioneeredin1960sacademia,thehighprocessingandtech-
nical demands of physical modeling kept the technique out of wider
musicaluseuntilthe1990s,whenitmadewavesininstrumentssuch
asYamaha’sVLseriesandKorg’sProphecy.
etechniquefoundearlyuseintherealisticsimulationofacoustic
instruments—atoughtaskforthemorestaticsynthesisandsampling
techniquesofthetime. atsameearthboundtendencymakesphys-
ical modeling uniquely able to create wild, dynamic, unprecedented
sounds,butinamannerthatremainsfamiliartoourear.Asourcom-
putersgrowfasterandourmodelsmorerefined,moreandmoreofthe
languageofthephysicalworldislaidopenforustoexplore. Andexploit.
ARoseisaRoseisanEquation
egoings-onofthephysicalworldcanseemimpossiblydetailedand
organic; more the realm of poetry than math. However, the efforts
ofphysicistsandmathematicianshaveshownusthatmuchofnature
canbedescribedquiterealisticallyinequations—mostoendifferen- Nobodyreallyknowswhytheworldis
tial equations. In our case, creating such an equation lets us use the quantifiableinthisfashion,butitsure
comesinhandywhenwewanttodesign
thingsweknowaboutthephysicalpropertiesofanobjectasrulesto
bridgesthatdon’tcollapse,bouncycastles
predicttheoutcomeofexcitingthatobjectwithagivensound(aswe withtheperfectrebound,ordronesthat
candeliverapizza.
doinKaivo’sRESONATORandBODYmodules).
Gettingtheresultswewantisjusthalfthefun.Oncewehaveaphys-
icalmodelthatsatisfiesourinitialgoals,it’sopenseason. Wecanadapt “Whyyes,I’dlikemyviolin’sbodyto
themodeltochangeitsproperties,itsbehavior,andthatofourinterac- changesizeandshapeasIplayit.You
candothat?Wow.Canthestringsran-
tionswithit. InKaivo,wecanmodulatethesepropertiesinrealtime,
domlyoscillatebetweengutandsteel,too?
openingawholevaultoffreshnewtimbralandexpressiveabilities. Great!”
IWantMyFDTD
Perfectlymodelingreal-worldhappeningswithmathisquitethetrick
initself,andutilizingsuchhyper-detailedmodelsinrealtimehaslong
been impractical, given the limitations of DSP chips and computer
poweringeneral. Giventhat,mostphysicalmodelinginstrumentsso
farhavereliedonasimplifiedtechniqueknownasDigitalWaveguide
Synthesis.
DigitalWaveguideSynthesisreliesonthefactthatsomeaspectsof
thebehaviorofacousticwavescanbesatisfactorilysimulatedwithsim-
pledelaysandfilters,ratherthanmorecomplexmath.
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iscutsprocessingexpenseconsiderably,albeitwithcompromises
inaccuracyandflexibility. Ingoesyoursignal, outcomestheresult,
anditmaynotbejustwhatyou’relookingfor.
Today’scomputershaveplentyofpower,soitseemsnaturalthatwe
shouldmovetowardtechniquesthatgiveusmoreaccurate,moreflex-
iblemodels.atiswhywechoseFinite-DifferenceTime-Domain(or
FDTD)asourmodelingmethodforKaivo.Withoutgettingtootechy,
FDTD lets us make more natural-sounding, accurate models to play
with. Italsogivesustheabilitytofeedsignalsinandoutofthemodel
atanypoint,andmakelocalizedbehavioralchanges,toboot. Inthis
way, tonalvariationsabound, andthedegreeofcontrolavailableisa
beautifulthing.
emostbasicFDTDequationusedinKaivoisthe1Dwaveequa-
tion. e motion of a string model, or the air pressure gradient in
a modeled tube can be expressed as a single value distributed across
space;soforthosemodels,weuseaone-dimensionalequation.
Whenwemoveonto2Dwaveequations,we’reabletomodelthebe-
haviorofobjectsthatrequiretwodimensionstodescribe(suchasdrum
heads or cymbals). We can finely control resonant properties across
themodeltosimulatephenomenasuchasthelocalizeddampingeffect
onacymbal’svibrationwhenit’smountedonastand. Whenwewant
tomodelshapesthatmoveinthreedimensions(suchasabox),Kaivo
usessomeFDTDmagictofolda2Dmodelintothedesiredshape.
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ALittleSomethingExtra
BothRESONATORandBODYfeaturenonlin(shortfornonlinear)di-
als. Sowhatdoesnonlinearmean? Anysoundcanbedescribedasa
sumofsinewavesatdifferentfrequencies.Wecallthesesinewavesthe
sound’spartials. Alinearsystemcanmodifyasoundbychangingthe
loudnessofeachofitspartialsovertime.Butwhatitcan’tdoischange
thefrequenciesofanyofthosepartials.
Someexamplesoflinearsystemsarevolumecontrols,EQsandeven
simplereverberators.AnEQcanlowersomepartialsbutnotothers;a
reverbcanextendmanypartialsintolongtails.Butneithersystemwill
introducepartialsatnewfrequencies.eonlyfrequenciesthatcanbe
outputfromalinearsystemaretheonesthatgointoit.
InthecaseofKaivo,nonlinearitiesrefertothetough-to-modelid-
iosyncrasiesinherenttoreal-worldobjects—aspectsoftheirbehavior
thatdonotcorrespondneatlytosimple,sleekalgorithms. ese“im-
perfect”propertiesareimportanttothenaturaljenesaisquoiofthe
objectsweseektoemulate,butarereallyonlybeginningtobeunder-
stood(andmodeledforourbenefit).
enonlindialoneachofourphysics-basedmodulesistheretoin-
jectalittlesonicspice, essentiallyemphasizingthenonlinearaspects
ofeachmodel. Atlowsettings,itcanaddjustalittlesomethingextra,
enrichingsignalsinaeuphonicway.Crankit,andthingscangetpretty
out-of-hand.Howmuchspicetouseisapersonalmatter,sogivenonlin
aspin. Degustibusnonestdisputandum.
For more details on physical modeling and using it in Kaivo, see
theRESONATORandBODYsectionsofChapter3,“Kaivo: Moduleby
Module.”
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