In what sense can bodies and instruments be said to form spaces?

The following is taken from the introduction of my 2014 master's thesis which can be found in full here:

My recent works begin from two fundamental precepts of instrumental performance practice:
    •    Sound and movement are fundamentally linked.
    •    Instruments, as architectures and as histories, condition movement along their surface.
The first statement regards bodies and their kinetic potentials, the expressive power of movement itself, and the intimate relationship of gesture to timbre.  In practice it requires an identification of all the relevant ways a body can move in a given space, which opens the possibility of the body as an observed system, and thus a target for modelling activity (Abraham, Shaw; 1992). The second statement regards objects within the context of subjects, the reciprocating intensity of that relationship, and the topological and historical realities of both.  It implies an acknowledgement of certain topological restrictions that mark points of resonance constituted from the design and construction of a given instrument, shaped by pedagogy and put into practice by a given repertoire. It asserts instruments as spaces in themselves, not as inert receptacles subject to imposition of our sonic whims but as agents mediating the dialogue between sound, history, and us.    
Implicit in this assertion of instruments as spaces is an acknowledgement of the possibility that a given instrument can change, not necessarily in terms of literal construction (although clearly this is also the case: range extensions, amplification, various preparations), but in terms of a shifting ontology of instrument surface.  For example we can ask if a given piano in performance of Beethoven’s Piano Sonata no. 17 in D minor is the same piano in performance of John Cage’s Etudes Borealis.  The piano is of the same parts, mechanisms and construction, but what has changed?  What changes is how we think in the context of piano surface, and the privileged points of attraction that thinking creates. I would propose that in altering our interaction with the instrument we alter the instrument itself.  The act of composing is simultaneously an act of reframing instrumental space by shifting points of attraction along its surface.
Dislocated and dissociated by language or culture or economy into the specialised ghettos of sex and mind, Soho and Bloomsbury, 42nd St. and W. 40th St., here is where my body tries to rediscover its lost unity, its energies and impulses, its rhythm and its flux. (Tschumi, 2001, 39)
At this point I can identify the performer/instrument assemblage as a symbiosis of two interdependent observed systems, each subject to change, each system exerting some force on the other which is in turn reciprocated, each system affording new realities for itself and its counterpart.  Additionally, and crucial for a compositional practice extending from these precepts, both of these systems are subject to modelling in the genesis of new works.  Through modelling techniques gestures emerge by direct manipulation of the materials themselves, via mechanisms immanent to the body and to instruments.  The fuel for this genesis is difference: the performer/instrument assemblage is conceived as a plane of converging heterogeneous continua, defined by ordinal relations, diverse rates of change, and rules of combination that are imposed to ensure that various parameters are linked by their differences (De Landa, 2002).
By extension of the initial precepts, my recent practice is influenced by choreographic, and architectural, as well as musical discourse.  Through choreography we can access insights into the potentials of human movement and reframe how we think about gesture.  Merce Cunningham sought to liberate movement from representational and historical referents, and decompose it into multiplicities (Gil, 2002, 121).  In William Forsythe’s work, dancers’ bodies ricochet into oblique fragmentation “by sending the eyes in one direction, jaw in the other, rib cage in one direction, hips in the other” (Casperson, 2001, 97).  What was revelatory in this discourse for my practice was the liberation of bodily movement from the instrument; that instrumental technique often forces the body into a relatively narrow gestural grammar when compared to what the body is actually capable of.  Subsequently the body’s degrees of freedom are decontextualised from traditional playing techniques, allowing me to write the technique itself when movement is re-contextualised into instrumental space.  This is instrumental technique not as typological and discrete but as emergent from more fundamental forces such as intensity of movement and pressure.  Timbre in my practice is not cosmetic; it is not a condiment applied to a greater construction of pitch and rhythm structures, but is itself the subject of the work.  The hypothesis is that in composing movement itself I can access timbre in an intimate and direct way, previously unavailable in conceptions of sound-objects and techniques as typological and readymade.  
In his paper on architectural sequences, Bernard Tschumi highlights three relations: space (S), movement (M), and event (E) (Tschumi, 2001).  For the purposes of making pieces I propose a simple algebra among them:
(S)pace + (M)ovement = (E)vent
In Tschumi’s writings there is an advanced discourse on the intense reciprocal relations between architecture and event.  Not only do we act upon architectural spaces, but additionally our actions are conditioned by the architectural object’s own mechanisms: a door implies the movement of a body through it (Tschumi, 2001) the same way that a tone hole on a flute implies the movement of air through it.  To this point, Tschumi gives the example of the “violence of narrow corridors on large crowds” (Tschumi, 2001, 124). In this way architectural design can be seen as a set of tools for structuring movements within a given space.
One could imagine a guitar where the twelfth position expands to many times its size while the first position contracts infinitesimally, or a piano that exudes a gravitational pull from the extreme low and high registers while a force of repulsion makes the middle nearly unplayable.  The implication here is instrumental surface as a nonmetric space, that is, one that cannot be defined by its distances because they remain unfixed and subject to change (De Landa, 2002). Nonmetric spaces are features of a neighbourhood topology: sets of points bound into neighbourhoods by relations of proximity and contiguity that may be stretched or compressed without changing in nature (ibid).  Through simple differential relations we can map one space onto another one, effectively redesigning instrumental surface, shifting points of attraction within the vector field.  This manipulation of an instrument’s inherent topological restrictions affords each work a set of characteristic gestural tendencies as movement is mapped along its undulating surfaces.