I first heard Alvin Lucier's "I Am Sitting in a Room" when Milkman Dan played it one morning on Radio 1190. The piece was made by recording a spoken paragraph, then recording the playback of the first recording, then recording the playback of the second recording, and so on, and then splicing all the recordings together. As Lucier narrates: "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..."
After a while the sound gets warbly, tonal, as certain frequencies get stronger and stronger. It's the audio equivalent of pointing a video camera at its own display (q.v.).
In collaboration with Frank Kwiatkowski I made a recording in the style of "I Am Sitting in a Room." In it, I read from the beginning of Richard III and Frank reads a selection from Huckleberry Finn. It was recorded in my apartment, which is mostly unfurnished and therefore echoey, on a Sunday night with little road noise outside the window.
Listen/download. 7:21 playing time. In the public domain.
Audacity's spectrum graph reveals that the resonant frequency of my apartment is 310 Hz, or about D♯.
Here's an earlier prototype we made. 9:10 playing time.