Decay Music is the 1976 debut album by Michael Nyman, released on Brian Eno's Obscure Records music label. The two works on the album, 1-100 (composed 1 December 1975) and Bell Set No. 1 (1974) are both built around the musical concept of decay. Both of these experiment with percussive, long decay musical forms. 1-100 is played at half the speed it was recorded. It was written for Peter Greenaway's film of the same title, but rejected because it was too long. It was inspired by Frederic Rzewski's Les Moutons de Panurge, which Nyman often played with the Scratch Orchestra.
The album was first issued on compact disc on March 29, 2004, by EMI/Virgin. The original full-speed recording of 1-100 is included as a bonus track.