Write a process piece that is simple enough to fit on a postcard. The piece should follow the guidelines set out in Reich's article Music as a Gradual Process. Once the parameters of the process are set up there should be no further compositional/performative decisions that alter the process.
You may use any combination of text, pictograms, notation, etc. to compose the piece, but the instructions should be very simple and direct. Aim for an absolute minimum of instruction that results in maximum sonic complexity.
You can refer to the instructions for Pendulum Music by Steve Reich, or to Jim Tenney's Postal Pieces for inspiration:
Tenney - Postal Pieces-1.pdf
Pendulum Music, for microphones, amplifiers speakers and performers
Three, four or more microphones are suspended from the ceiling or from microphone boom stands by their cables so that they all hang the same distance from the floor and are all free to swing with a pendular motion. Each microphone’s cable is plugged into an amplifier which is connected to a loudspeaker. Each microphone hangs a few inches directly above or next to its speaker. Before the performance each amplifier is turned up just to the point where feedback occurs when a mike swings directly over or next to its speaker, but no feedback occurs as the mike swings to either side. This level on each amplifier is then marked for future reference and all amplifiers are turned down.
The performance begins with performers taking each mike, pulling it back like a swing, and then holding them while another performer turns up the amplifiers to their pre-marked levels. Performers then release all the microphones in unison. Thus, a series of feedback pulses are heard which will either be all in unison or not depending on the gradually changing phase relations of the different mike pendulums. Performers then sit down to watch and listen to the process along with the rest of the audience. The piece is ended sometime shortly after all mikes have come to rest and are feeding back a continuous tone by performers pulling out the power cords of the amplifiers.
Steve Reich 8/68 revised 5/73
Pendulum Music (Links to an external site.)