I knew of a art/ambience band who did a conceptual piece. It was called, '1 Note, 24 Hours'. A group of musicians took shifts in playing only the 'E' note over an entire day. At around the 18th hour, a member of the group, having just arrived for his shift, took a guitar, and played an E chord, which includes the notes, E, B and G#.

After that, the last 6 hours seemed to drag somewhat.