"surfaces..." is for a group of electric guitars (six in this performance) playing feedback only. The feedback pitches are all harmonics of whichever string is vibrating: which is in itself indeterminate as for most of the piece all the strings are free, in the opening 6 minutes only the low E string is free (see the felt "mutes" on the guitars). The guitars change feedback pitch by moving. Changing the relative position between guitar and amplifier alters the phase relationship and allows a different harmonic to emerge. The score does not specify pitches, but simply asks the players to (1) allow a pitch to emerge and hold it, (2) very slowly change to a new pitch, (3) try to return to the previous pitch. Players keep trying to set up slowly oscillating pitch patterns but the indeterminate nature of the feedback interferes with this. The players are also detuning the strings intermittently throughout the piece: players work to an grid of approximate timings, with rest points built in for detuning. What starts as a unified E harmonic spectrum slowly denatures into an inharmonic mass.
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