I am sitting in a room (1969) is one of composer Alvin Lucier's best known works, featuring Lucier recording himself narrating a text, and then playing the recording back into the room, re-recording it. The new recording is then played back and re-recorded, and this process is repeated. Since all rooms have characteristic resonance or formant frequencies (e.g. different between a large hall and a small room), the effect is that certain frequencies are emphasized as they resonate in the room, until eventually the words become unintelligible, replaced by the pure resonant harmonies and tones of the room itself. The recited text describes this process in action—it begins "I am sitting in a room, different from the one you are in now. I am recording the sound of my speaking voice," and the rationale, concluding, "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," referring to his own stuttering.
Lucier had also specified that a performance need not use his text and the performance may be recorded in any room. The composer himself has recorded the piece in at least one room he did not find aesthetically acceptable.
In its repetition and limited means, I am sitting in a room ranks with the finest achievements of Minimal tape music. Furthermore, in its ambient conversion of speech modules into drone frequencies, it unites the two principal structural components of Minimal music in general. —Strickland (2000), 
The first recording of I am sitting in a room was made at the Electronic Music Studio at Brandeis University in 1969.