half closed loop an improvisation environment for...

Half-closedLoop—animprovisationenvironmentforcoveredstringandperformer

TillBovermann

UdKBerlin,Berlin,Germanyt.bovermann@udk-berlin.de

Abstract.Theperformance“half-closedloop”isatakeonaninstrumentforastorytellingimprovisation.Bymeansoffeedbackinductiononvariouslevels,particularlybyacustominstrumentconsistingofastringinabrasspipeandawoodenboardwithattachedstructure-bornedrivers,thedesign’sideaistonotonlyallowtheperformertoproduceabroadrangeofmusicalexpressionsbuttoalsointegrateelementsofinstabilityintotheperformance.Beingdesignedasanopensystemwithasignificantamountofcomplexityinroutingandcontrol,theinstrumentletsperformerandinstrument“fuse”intoonemeta-systemofhuman-instrumententanglement.

Keywords:control,interaction,performance,feedback,analogue,digital,improvisation,wavesets,resynthesis,musicalinstrument

Figure1:“Half-closedloop”:Setup(a),Performing(b)anddriverarrangement(c).

IntroductionImprovisationisthe-possiblycomplex-processinwhichperformerscontributetoapiecebyselectingwhileplayingfromanextensiverepertoireoffiguresandphrases.Theirchoiceisbasedonpersonalinterpretationsandbiasaswellasthedirectiontheperformerintendsthepiecetoadvance.

Atthesametime,theformofaninstrumentforimprovisationinfluencesthesoniccharacterofaperformancethoroughly.Itsfeaturesandcharacteristicsdeterminehowmucheffortittakestocarryoutanintendedexpression.Theyhaveacrucialimpactonwhattheplayerdecidestoplay.

Oneformofsonicimprovisationcanbenamed“sonicstory-telling”.Thelistenerisinvitedtoclosehereyesandlistentoasoundworldtotakeshape.Morequitepartsalterwithloudandintensephrases,parallelstreamstaketurnsinleadingorfollowingthesoundscape’sgestalt,whilesurprisingelementsappearandhavetobeintegratedintothesonicworldbyboth,theperformerandthelistener.

Theperformance“half-closedloop”isatakeonaninstrumentforsuchastorytellingimprovisation.Itsintentionistonotonlyallowtheperformertoproducearangeofphrasesandmusicalexpressionsbut,toaprominentpart,tointegrateelementsofinstabilityintotheperformance.Theseinstabilitieshelpkeepingtheperformeralert,herstrugglewithplayingtheinstrumentturnsintoaninherentpartofthestorytellingprocessitself.Beingdesignedasanopensystemwithasignificantamountofcomplexityinroutingandcontrolletsperformerandinstrument“fuse”intoameta-systemofhuman-instrumententanglement(Hinrichsenetal.2014).

Components

Figure2:Routingandcomponentsof“Half-closedloop”.Notethatthecomponentsintheupperleftaredigitalimplementationsthatarecontrolledwithamixer-likeinterface.

“Half-closedloop”1consistsofseveralparts,eachservingaspecificpurposefortheimprovisationsetup.Thetwovisuallymostprominentelementsareabrasspipeandahardwoodboard.Togethertheyassembleafeedbackinstrument(seeFigure1):Thebrasspipehasanaudiotransducerattachedtooneofitsendsandcontainsatightenedstringthatisinaccessiblefromtheoutsideduringperformance.Thepipethereforeservesasthepassiveelementofthefeedbacksystemsinceitcapturesvibrations.Withtwostructure-bornedriversattachedtoitsfloor-facingside,thehardwoodboardcanberecognisedastheactiveelement.Sittingonfourrubberfeet,itsvibrationsarepickedupbythebrasspipe,whenplacedonitssurface.

Thesignalfromtheaudiotransducerissenttothecomputerwhereitisprocessedbyalow-passfilterandadigitalreverb.2Additionally,itisfedintotheanalysispartofaWaveSetre-synthesisengine(deCampo2011)(Wishart1994).Thesoftwaresetupeventuallyrendersastereosignalcombiningthefilteredpipesound,tworeproductionpartsoftheWaveSetre-

1Adocumentationvideoofoneofthefirstsessionswiththesystemcanbeviewedathttps://vimeo.com/156190237.2JPVerbbyJulianParker,http://tai-studio.org/index.php/deind-ugens/.

synthesisengine,andabasssynth(afeedbackFMoscillatorwrappedinaladderfilter).Therenderedsoundisthenpassedtoananaloguematrixmixer(Collins1997)3bywhichitcanbeenrichedbyananalogueeffectboxcontainingaladderfilterandaJFETdrivecircuit.4AllsoftwarepartsareimplementedinSuperCollider.5

Withthissetofsoundgeneratorsandshapers,“half-closedloop”providesabroadrangeofsonicexpressionstotheperformer.Itssonicgestaltisbasedonenvironmentalaswellasartificialparts(audiotransducervs.synthesiser)whileatthesametimebeingrootedinmultipledomains;analogueandacousticfeedbackisopposedbydigitally-soundingre-synthesisofpreviouslyplayedelements,whichallowsforsemi-automatedregularpatternsbasedonthesoniccharacteroftheotherelements.Atthesametime,percussivesoundscanbecreatedviaphysicallyknockingthepipeortheboard,whereastheaudiofeedbackallowstocreatesustainedsounds.Allthosesoundscanbelinearlyaswellasnon-linearlyalteredandtime-smeared.

InteractionCreatingandplayingadynamicsoundscapewithseveralacousticlevelsischallengingforoneplayer.Afterall,thenumberofitemstocontrolislimitedbythenumberofhandsandfingersoftheperformer.Oneapproachtolowertheamountofcontrolswhilestillkeepingasignificantamountofcomplexityistheuseofcross-linkingmappingmatricesasitisdescribedbydeCampo(deCampo2014).Theapproachusedin“half-closedloop”istooutsourcedecisionprocessestothesystemitself:Bybeingpronetoexternalinfluencessuchasvibrationsintheroom,thesubliminalmuscletremoroftheperformer’shands,orjustminimalposturechanges-e.g.,whenturningaknobonthematrixmixerthesystemchanges,resultingina(smallormoresevere)variationofitssonicoutput.

Allparametersofthedigitalandelectronicsoundshapingcanbeaccesseddirectlyviadedicatedknobs,buttons,orfaders.Thisimmediacyinsoundgenerationcombinedwitharelativelysimpleplayinginterfaceallowsforfastreactionstothedescribedunforeseenevents.Itissupportedbyvibrationalfeedbackthroughthehardwoodboard;changesinthesystemcanbefeltmuchearlierthanheard.

Acknowledgements.TheusedRTWaveSetUGensetwasimplementedbyFabianSeidl.Therealisationofthe3DMINproject(Bovermannetal.2014),andthusthispaperanditsrelatedresearch,wasfundedbytheEinsteinFoundationBerlin.

ReferencesBovermann,T.,H.Egermann,A.Foerstel,A.Hinrichsen,D.HildebrandMarquesLopes,A.Pysiewicz,S.Hard-jowirogo,S.Weinzierl,andA.deCampo.2014.“3DMIN–ChallengesandInterventionsinDesign,DevelopmentandDisseminationofNewMusicalInstruments.”ProceedingsofICMC/SMC.Athens:NationalandKapodistrianUniversityofAthens.

Collins,N.1997.“Gain:ReflectionsonDavidTudor.”MusikTexte.

deCampo,A.2011.ChapterMicrosoundofTheSuperColliderBook,editedbyS.Wilson,D.Cottle,andN.Collins.MITPress.

deCampo,A.2014.“Losecontrol,gaininfluence-ConceptsforMetacontrol.”ProceedingsofICMC/SMC.Athens:NationalandKapodistrianUniversityofAthens.

Hinrichsen,A.,S.Hardjowirogo,D.HildebrandMarquesLopes,andT.Bovermann.2014.“PushPull.ReflectionsonBuildingaMusicalInstrumentPrototype.”ProceedingsoftheInternationalConferenceonLifeInterfaces.

Wishart,T.1994.AudibleDesign:Aplainandeasyintroductiontopracticalsoundcomposition.OrpheusthePantomimeLtd.

3Analoguematrixmixerasdescribedathttp://tai-studio.org/index.php/matrix-mixer/4MoogMFDrive.5SuperCollidercanbefoundathttp://supercollider.github.io