These duos were followed by a chamber work (Machine Language, also by Trueman) for electric violin with acoustic violin, cello, and percussion.   One of the intentions of the piece was to explore how we could expand the sonic palette of a conventional chamber ensemble with an electronic instrument without destroying its rich acoustic surface.   We were also hoping to maintain the familiar modes of interaction between chamber musicians, where sound localization is important and music-making as activity (apart from performance) is (or was) of primary interest.   The success of this endeavor has encouraged us to pursue these possibilities further and has inspired other composer/performers to adopt spherical speaker arrays for their own compositions.

One example is the composer and electric guitarist Steven Mackey.   Mackey’s Troubadour Songs (for string quartet and electric guitar), though successful, have proven difficult for obvious reasons blending the electric guitar and string timbres while maintaining comparable levels is difficult.   Through the use of a new spherical speaker, Mackey has been able to address this problem in both performance and recording; in a recent session, the pieces were recorded in a large hall with open-air microphone placement (conventional for string quartet recordings) and close-mic’ing of the guitar amplifier was unnecessary.

This new "voice" for the electric guitar figured heavily in Mackey’s composition of a new concerto (Tuck and Roll) for electric guitar and orchestra, premiered in April 2000.   Mackey composed the work with these new speakers in mind, and conceived of the electric guitar as a member of the orchestra.   He adjusted equalization settings, quantities and qualities of distortion, chorus and other effects to create a unique new orchestral voice that could match the various instruments of the orchestra in different combinations.

Mackey’s sphere (14-inch diameter, with twelve 4-inch coaxial drivers distributed symmetrically over its surface), is stereo (a plane divides the interior of the sphere, and the two halves are wired separately).   With the orchestra, he used two spheres, arranged as in Figure 2.

Stage Setup.  Arrows point toward US Enclosure Loudspeakers.

The sphere next to Mackey was the primary sphere, the second providing slightly more volume to match the orchestra.   Both were oriented so their two channels could be adjusted "front and back;" the orchestral, "back"-side was initially set rather loud, while the orchestra learned the piece, but as they became more familiar with it, the back-levels were attenuated.

Mackey found that adjusting the relative gain of the front and rear hemispheres had a significant effect on the orchestra’s performance; initially, with the back-side rather loud, the orchestra overplayed, trying to match the level of the soloist- after softening the back-side, the orchestra played more sensitively, which afforded the soloist (Mackey) a greater dynamic range.   In either case, the spatial radiative qualities of the front-side kept the electric guitar in the natural acoustic space, and negated any need for conventional P.A.-style amplification.

Audience feedback consistently indicated that the acoustic effect that Mackey sought- a convincing blend of electric guitar with orchestra- was successful; listeners and orchestra members felt that the guitar "blended effortlessly," that it seemed to "belong."   Ironically, this was initially troublesome to some listeners (and the conductor) whose conception of the electric guitar as musical icon- loud, macho, aggressive, epitomized by the Marshall Stack or Fender Twin amplifiers- was quite different than Mackey’s approach.   For these listeners, there was a kind of cognitive dissonance created by their expectations of the "electric guitar" and Mackey’s new instrument.   For most, however (including the conductor, Michael Tilson Thomas), this frustration eventually gave way as the instrument and composition asserted their own musical personalities.

Making Electronic Ensembles More Intimate

The electronic improvisation duo "interface" (Bahn and Trueman) began as a purely acoustic duo, improvising informally in living rooms, recording studios and other small spaces.   As we integrated electronics and computation into our improvisations, our conventional sound system grew, eventually completely obscuring our acoustic beginnings.   In our most recent season, we replaced our P.A.-style system with a set of five spherical speaker arrays of various sizes, including two 14-inch spheres, a 12-inch sphere, an enormous 22-inch sphere, and an 8-inch tweeter-ball.   These speakers, strewn about the stage in various configurations, function much like instrumental sources and create a sound field somewhat similar to a conventional chamber ensemble.   The spheres localize our sounds, providing distinct points on stage for listeners and performers to grasp, yet also fill spaces and encourage listeners to walk among us; the typical plane of separation created by stage and P.A. system is non-existent.   We find that this sound system drastically affects the way we play our electronic instruments, encouraging us to play softly and explore spare textures.   It also feels familiar, reminding us (distantly) of our earlier, more "acoustic" improvisations.

Bahn has used a hybrid system in performance, combining spheres with conventional speakers.   Four stereo spheres are set amongst live performers amplifying and processing their sound.   Most often, the sound sent to the spheres has a consistent routing, giving the spheres a particular sonic on stage and within the ensemble.   As with all applications discussed in this presentation, this integration of natural and electronic sounds can be strikingly natural and effective.   Signal processing representing impossible acoustic situations, extreme delay, reverb or other effects, can then be cast into a conventional sound system at the back or sides of the performance space.   The hybrid approach allows manipulation of both individual points of sound within natural sonic space, and the altered perception of space provided by conventional sound systems.

Interdisciplinary Applications

Streams is an interactive sonic landscape formed (by Bahn) in collaboration with dancer Tomie Hahn.   Custom sensors capture the tilt and movement of her arms and record pressure of touch on a small resistor in her palm.   A MIDI radio transmitter sends this information back to a computer-performance system where it is mapped into interactive synthesis and signal processing designs within the MAX/MSP environment.   The sonic landscape is displayed using three spherical speaker arrays placed behind her, to her left, and to her right.   Discreet aspects of the composition are uniformly cast into unique speaker arrays forming individual, physically locatable "identities" within the sonic design and installation of a performance.   Signal processing algorithms- granular synthesis, delay loops and reverberation- can be activated by the dancer during a performance.   These altered sounds are cast into spatialization algorithms that pan and distribute sonic grains between spheres.

Conclusions and Future Work

Spherical speakers provide a compelling new "voice" for electronic sound, one that is particularly compatible with acoustic instruments and well suited for intimate spaces.   SenSAs further enhance these qualities and create a new class of electronic instrument.   This work also suggests a more general approach toward working with electronic sound and human-computer interfacing, one which emphasizes outward, multi-directional (though not necessarily symmetrical) diffusion with proximal, physically motivated sensor structures.   In the future, we plan to pursue some of these possibilities, including designs that are more idiosyncratic, asymmetrical, yet retain some of the diffusion qualities of spherical speakers.   As with traditional instruments, these structures have unique acoustic characteristics that may be exploited musically, diversifying the voices of electronic sound.