Half-closedLoop—animprovisationenvironmentforcoveredstringandperformer
TillBovermann
UdKBerlin,Berlin,[email protected]
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.
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