About feedback as a form of material-indeterminacy where forms can emerge through the intersection of performance and structuring.
My approach to feedback is fundamentally about materiality, indeterminacy, emergence, and improvisation (responsiveness to contingency). Feedback is always material. The self-sustaining vibration of a body (wood, metal, air, etc) arising from a particular configuration of both the material-spatial and the 'energetic' (Simondon  2005) that affords continuous flow along a path of resonance. Feedback arises as the path of least resistance in a given configuration, which opens the door for composition as a manipulation of configurations. My compositional concern is always with pitch—or pitch-timbre complexes like multiphonics—so my use of feedback is about how pitch emerges from the interaction of materiality and performance rather than being imposed from an external system (e.g. tonality, or equal temperament). Performance here is the performative and responsive altering of configurations and energetics in real-time. This is not about how the performer controls the feedback to reach a fixed and predetermined state, but rather how they manipulate the environment to allow indeterminate and emergent relationships of pitch. The scores here define relationships rather than specifics, leaving the performer to create states in which those relationships can emerge.
One of the research journeys outlined here is about ‘what happens’ to ‘what emerges’. This relates strongly to anthropologist Tim Ingold's concept of 'wayfaring', of following emergent paths. Ingold describes the wayfarer as having "no objective save to carry on, to keep on going. But to do so, his action must be closely and continually coupled with his perception. . . . [wayfaring is] not so much intentional as attentional. It thrusts the follower into the presence of the real" (Ingold 2015, 132–3, emphasis in original). In my work, the act of compositional research is partly in trying to find territories rich in paths that might be followed, and in developing techniques for following these paths. I am a pitch-centric composer with a love of emergence, so these techniques are often to allow the specifics of emergent pitches to become meaningful in the unfolding compositional structure, without determining them in advance. In other words, while the feedback pitch is indeterminate, once it does emerge it has an identity, and how does that identity then exert some level of structuring control on the composition, become part of a larger relationship than simply its own becoming. I want to avoid the ‘emergent’ or ‘indeterminate’ being synonyms for ‘arbitrary’ and ‘inconsequential’. Since in most cases (but see below for exceptions) the pitches emerge from a materiality that does not change during performance, then the emergent pitches act as a map or trace of that specific materiality. In Heideggerian terms, the music is an act of revealing or ‘unconcealing’ a material truth that is anything but arbitrary, but that resists singularity and definition, being open, layered, and vibrant.
As a guitarist coming from MBV and Sonic Youth, I’ve always used feedback, but only in recent years have I approached it as almost the perfect ground for my interest in indeterminacy, contingency, and materiality. To give a brief nod to context, there is a strong debt here to the musics of Alvin Lucier, Nicolas Collins, David Tudor, Eliane Radigue, Adam Basanta, Steven Vinkenoog, Alice Eldridge, Stephen Cornford, John Butcher, and Cathy van Eck.
Here is a brief description of the formal works I’ve written that start to explore this.
I draw a distinction in composing these pieces between ‘point’ and ‘field’ systems; and in the case of feedback, these are all continuous/non-discrete fields, unlike, say, a piano which has a discrete field of pitches in its keyboard.2
Point systems have no changing variables so are the most simple version, usually used compositionally for short studies to test an idea. For example, a single electric guitar at a fixed point/position relative to the amplifier, and with a fixed gain. Composing for a point system can mean specifying an outcome and configuring the point to ensure that outcome, or it can mean configuring the point according to some other decision framework (logical, intuitive, whatever) and seeing what emerges. For example, if on a violin string I want to hear C4 then I configure the point (finger position, assuming ‘normal’ bowing for C4) that will produce C4. Alternatively, I could ignore the imposed universal system of 12TET pitches and instead configure the point with reference to something else, such as generating some arbitrary distance from the nut to finger-position to produce an arbitrary pitch (again assuming ‘normal’ bowing).
A violin string is a useful example but is relatively predictable because it is linear. The same comparison in a feedback context would be quite different since feedback is sensitively dependent3 on parameters of the room and the equipment, often in nonlinear and hysteretic ways. The same arbitrary generation of parameters in a feedback context will produce ‘something’, but like a strange-attractor (see figure 1) it is only through repetition that structure emerges, only by repeatedly stepping through the same non-linear space are elements of structure ‘unconcealed’. The combination of repetition and non-linear structure makes this a space for responsive exploration. This is what interests me about feedback and indeterminacy, not simply that it is hard to control, but that there are hidden relationships that can be revealed through performance and allow the material to express itself. The fact that the system is unknowable in advance (indeterminate) does not mean that it is arbitrary. There are relationships and principles that can be explored in performance to both reveal structures and modify them that can speak to that specific moment and context. By performing a point system, the characteristics of the whole field start to be sketched out.
Repetition across many points in performance then becomes exploration of a field system, which is an order of magnitude greater than point systems in terms of potential for complexity because they have changing variables along different planes. This also means that fields are more open to responsive performance as those variables are explored in real time. For feedback systems, I work with two planes which I will call the spatial and the energetic (after Simondon). To return to the simple violin example, a single string is a horizontal plane where, between the nut and the bridge, there are infinitely many possible positions on a linear scale of pitch. The violin’s vertical plane is that of bowing, which is much more complex and multivariate (resulting from the interaction of bow speed, position, pressure, angle, etc) but can reasonably be reduced to a single plane of intensity. This plane is significantly less linear than the horizontal, but can be characterised as having a ‘safe’ central zone containing (a) different sub-zones that affect timbre but not pitch, and (b) zones at both ends where extreme highs and lows of any parameter can produce both extreme timbres but also changes of pitch (harmonics, subtones, multiphonics, etc).
In a feedback system the spatial plane can be operative on whatever scale of distance suits the system; the material, the gain structure, etc. Assuming a certain tuning of the system to allow flexibility in performance, movement around this plane—by the system-input (guitar-pickup, microphone, etc)—will change the feedback pitch. The topology of pitch across the space is closely related to the topology of resistance because points in the field are more or less sensitive to change. The larger the spatial plane, usually the more possibility for different scales of sensitivity: some points may have a single dominant pitch, others may afford localised micro-movement that allows for competing pitches to be held in balance or played tipping points to be explored.
The other plane is that of energetics, which in feedback is the gain-structuring. Changes in the energetic plane alter sensitivities. A piece that uses only the energetic plane can be exemplified by a single guitar fixed in position but with gain control, in which case the energetic plane will again have points of immediate rupture and also delicate tipping points; all of which have a hysteretic component. Gain alterations may also interact with sensitivities in the spatial plane if both are in play, leading to a complex set of relations to be explored in composition and performance. In the pieces discussed below, the energetic plane is rarely used compositionally (though it features strongly in the initial setup and tuning-in to the system), but in future works it will come more strongly into play in compositional strategies.
The following sections discuss specific pieces with respect to spatial and energetic planes as compositional devices/constraints. While this can be read non-linearly, it’s worth bearing in mind that in most cases each piece builds on what was learned from the previous in how the planes have been implemented compositionally, and the narrative reflects this.
In Surfaces of Emergence, only the spatial plane is used compositionally. Players use gain control in a binary manner only, to mute the instrument in specific sections. Pitch is emergent from the movement of the guitar relative to the fixed amplifier. The global structure of the piece is fixed, with sections defined by clock-time, and actions defined in terms of which strings are available for feedback, as well as detuning actions (discussed below).
The interesting compositional act is in the local structure, which is created by pattern-forming from the emergent pitches through listening and careful exploration of the indeterminate spatial plane. The basic performance process is that the player allows a stable tone to emerge, then makes small shifts to find another stable tone, before attempting to return to the original: see Figure 2 for score example. While this seems on the surface to allow only very simple patterns, returning to the original is not always simple. The relationship of feedback pitch to guitar position is real,4 but dependent on many factors. This includes the hysteretic characteristic of feedback systems; so the return may not be to the precise position required by that pitch, or the new pitch may be too dominant for that change of position to supplant it. As well as the position being friendly to the newly sought pitch, it is often the case that to allow a change it must also be unfriendly to the currently sounding pitch
This local structure of pattern-formation takes place over sections ranging from 1–10 minutes long, though averaging 2 minutes each. As the 30-minute piece unfolds, the players have breaks where they arbitrarily detune their strings, which moves the piece away from the dominant spectrum of E in which it starts, but also opens the possibility that random sympathetic resonant connections may happen across guitars as they are potentially influenced by each other’s strong pitches. This random detuning is a way to arbitrarily ‘reset’ the system, undermining the player’s map of the spatial plane they may have built up by this point in the piece. Reintroducing indeterminacy to the piece, but not quite a tabula rasa.
This is more like a body of practice than a specific piece, though it should in 2022 have some different instantiations as ‘pieces’. The key principle here is to use the spatial plane but extending the technique in Surfaces of Emergence by exploring strategies that are both more processual and more responsive (depending on collaborator). Initial experiments focussed simply on moving a microphone across a room relative to a fixed speaker. It was observed that for any given traversal of the space there was one or two pitches that recurred at more-or-less equidistant points from the speaker; with some more arbitrary-sounding pitches occurring between these points.
This video example shows the first composed version of this. Here the performer carries a DPA4006 omnidirectional lavalier microphone along a fixed path over a fixed duration; moving from the point where feedback begins, to the point where feedback becomes uncontrollable. This macro-process is repeated several times from different starting points to create a layered video of multiple feedback lines; which would be impossible to create with multiple performers. The process here is relatively strict—though my time-keeping in this proof-of-concept video was imperfect—to ensure the multiple performers are more-or-less equidistant from the speaker at the same time. However, this strict process is balanced by a more responsive and performative local process where each step on the spatial plane includes a careful ‘feeling out’ of the feedback by using the performer’s clothing as a damper, or the open hand as a reflector. The performer listens for emergent feedback and surfs that emergence to coax the feedback tone out, and avoid sudden explosions of feedback. In certain points along the walk, this local process supersedes the macro-process when there are several possible feedback pitches and the performer must choose which to favour.
This mixing of types of process is different to Surfaces of Emergence which aims for form-emergent patterns, because here the goal is to sustain a single line of strongest resonance as it changes across the horizontal plane. Since this 2016 proof-of-concept I have worked with movement artist Maria Kapsali on a more improvised implementation which includes a looser version of the Surfaces of Emergence pattern-forming algorithm as one of its techniques, but with the overall goal of improvisatory exploration of the space via feedback as a listening tool. Separately, I worked with musician Mauricio Carrasco on a more processual exploration of space where emergent pitch structures and listening are primary.
This piece uses electromagnetic resonators on a prepared piano, again using the spatial plane. Like Feedback Topologies this piece focusses on small movements, but with more emphasis on tipping points rather than stabilities. The piece uses modified guitar EBows on the prepared piano strings, with the performer alternating moving and listening to find positions on the string where tipping points between partials on the inharmonic spectrum can be found. Stable feedback pitches are discovered and gradually replaced via slow crossfades, beating-pitches, and other metastable phenomena. In the final section of the piece, the EBows are left in place while a stronger (mains-powered) custom resonator is used to excite and explore partials of the low strings of the piano; the lowest of which are inherently inharmonic.
This piece explores the spatial plane ever deeper, searching for further and further instabilities. In its concert form this works well, but the final-form of this piece is destined to be a durational performed installation, where the performer can truly take their time as they map out the metastable phenomena of the prepared piano. I hope to realise this in 2022.
This feedback clarinet (v.1) was built by Sam Underwood for my project The Garden of Forking Paths. This is a clarinet body with a loudspeaker installed at the barrel, and a microphone positioned somewhere else inside or outside the clarinet body: the default microphone is installed just below the loudspeaker, though this can be removed or muted. Additionally, the mouthpiece contains a breath controller which is mapped to the gain of the internal amplifier: the mouthpiece is completely separate from the body, so only breath pressure is meaningful in performance. The feedback clarinet is played through a mixer, often with more than once microphone attached, and may include onboard processing, especially reverb and compression/limiting.
While no formal pieces have yet been composed for this, the improvisations use both the spatial and energetic planes, and are leading towards scored compositions. The spatial plane has two manifestations here: the fingering configuration of the clarinet body (i.e. which holes are open or closed, altering the air-column resonance); and optionally one or more microphones may be placed external to the clarinet body, so moving the clarinet in space alters the feedback. The energetic plane is also used here, primarily through the mouthpiece breath-pressure sensor which controls gain (alongside a circuit to balance and offset gain if needed), but also there is the option of controlling the channel gain on the mixer in performance; whether to correct gain imbalances in the system, or to disrupt the system and break an existing pattern or dominant resonance.
Playing with a single internal microphone is relatively determinate. The basic spatial plane (simple unforked fingerings) produce repeatable pitches in a single register (though unrelated to standard clarinet registers and pitches), with more complex forked fingerings leading in some cases to indeterminacies. The energetic plane can produce register jumps and pitch changes if the gain-staging is tuned appropriately to align well with physical movement of the player. Once a second microphone is introduced, both planes5 increase in complexity and indeterminacy as the interactions multiply.
The improvisations documented so far have adapted strategies from all the other pieces here. Structuring through pattern-formation is achieved by finding stable pitches, but also by exploring beyond those stabilities in both planes, revealing metastable phenomena and unconcealing the materialities of the system. Current plans for compositions begin with studies that constrain the planes, and explore specific combinations of single and multiple microphones. Later pieces will be more exploratory, developing the pattern-forming algorithm from Surfaces of Emergence to also play a role in local structuring.
In this short text I have discussed four compositions of my own that all use feedback as a vehicle for exploring indeterminacy and emergence as structuring forms. The concepts of spatial and energetic planes are provided to group different types of interaction together. The spatial plane is the invisible network of feedback potentials explored through physical movement in a space of any size, and the energetic is the plane of the potentials themselves that is usually explored through alterations to gain-structure or materiality (altering resonant properties, and consequently the material's sensitivity to resonance).
The key point here is not to map these planes or to mine them for interesting sounds to be later sequenced into a 'piece', but that the responsive and performative exploration of these planes reveals feedback as a trace of the material-resonant, a revealing that interacts with score-based constraints to create emergent forms. The unconcealed forms of the network of potentials is globally indeterminate but can be locally uncovered through the process of exploration and a highlighting (through repetition) of specific properties; of which pitch is most immediate and important to me. All of these pieces do this in similar but different ways, developing techniques of what Ben Spatz refers to as the 'development and sedimentation of repeatable pathways of action', but always surfing an invisible edge where the repeatable revealing of a pitch falls into an epistemic space where exploration again takes the lead, moving back and forth across thresholds of stable and unstable knowledge.
Ingold, Tim. 2015. The Life of Lines. Abingdon: Routledge.
Simondon, Gilbert. (1964) 2005. Individuation in Light of Notions of Form and Information. London: University of Minnesota Press.
Spatz, Ben. 2015. What a Body Can Do. Abingdon: Routledge.