Apparently ‘performed’ really is the word to use, though many will argue that it doesn’t apply.
In 1969, Alvin Lucier ‘composed’ his best known creation ‘I am sitting in a room’. The concept itself is explained in its ‘lyrics’.
“I am sitting in a room different from the one you are in now. I am recording the sound of my speaking voice and I am going to play it back into the room again and again until the resonant frequencies of the room reinforce themselves so that any semblance of my speech, with perhaps the exception of rhythm, is destroyed. What you will hear, then, are the natural resonant frequencies of the room articulated by speech. I regard this activity not so much as a demonstration of a physical fact, but more as a way to smooth out any irregularities my speech might have.”
I decided that I would give this pioneering piece of tape music a try. This is 38 recordings of my voice, dwindling in quality with each subsequent recording.
As you might be able to see from the waveform, it’s quite obvious when each recording begins, as one microphone’s sensitivity was slightly higher than the other. However, I feel guiltless considering the variables that Lucier mentioned personally, such as moving the microphone, using instruments aside from the human voice etc.