According to the current Cycling 74 website:
M was "first published by Intelligent Music in 1987. In the 1980s, M
ran on four different computer platforms (Mac, Windows, Atari, and
Amiga), and had many fans all over the world.
M was quite different from any other music software when it first
appeared, but many musicians and composers were attracted to its
powerful implementation of the idea of interactive composition, where
you shape the music as you hear it unfold."
Download #1: version 2.5.5 of M from 1997 (PowerPC version only).
Image includes a PDF manual for version 2.5.
Download #2: version 2.2.4 of M from 1992, which can run in System 6
on a Mac Plus.
