Alvin Lucier’s landmark I Am Sitting in a Room (1969) vividly illustrates basic principles of architectural acoustics. By recording and then iteratively re-recording a short statement within the same room, the composition gradually changes until it reflects the resonant structure of the room itself. This 4 min video with excerpts from the full 45 min performance includes written commentary on the acoustical changes that has been helpful in illustrating its main principles in courses at McMaster.