Why is it called M?
The first name of the program as it was being developed was "Master Composer", then it was going to be called RMan, for "Random Manager."
Shortly before releasing the first version, the four original authors met with Christopher Yavelow and Curtis Roads, well-known writers in the computer music field, to see if they could help come up with a better name. All the things the program seemed to relate to began with the letter "M" -- MIDI, Macintosh, Music, Maestro so eventually Yavelow said, "Why don't you just call it 'M'?" There is a well-known movie called "M" starring Peter Lorre, but it has nothing to do with the program. Nor does a band from the early 1980s called M that had a hit single called "Pop Muzik."
Another possible coincidence or conspiracy is the multimedia company "M Factory" based in northern California that had an expensive software product called Mtropolis. M was first released with another program called Jam Factory. Currently mfactory.com links to a software consulting firm with the beautiful name of Overhyped Technologies.
What is the story behind M?
The first version of M was written for the Apple Macintosh starting in 1986 at a small company started by Joel Chadabe based in Albany, New York called Intelligent Computer Music Systems, or Intelligent Music for short. The goal of the company was to develop an 'intelligent musical instrument' that could take many forms, and M was the result of the exploration of a particular form that involved the manipulation of stored presets (called variables) using onscreen conducting gestures. It was designed to work with MIDI synthesizers. The authors were David Zicarelli, John Offenhartz, Antony Widoff, and Joel Chadabe. A preliminary version of M was released in late 1986 and version 2.0 in 1988. Version 2.0 was developed principally by David Zicarelli and contained an entirely new interface and many new features such as the Pattern Editor.
After the first version of M was released for the Macintosh, it was ported to other platforms. A version for the Atari ST was written by Eric Ameres. A version for the Commodore Amiga was written by Darien Fitzgerald that included an internal sampling synthesizer. Voyetra developed and marketed a version of M for the PC called M/pc.
Intelligent Music left the MIDI software business in early 1990. The Macintosh, Atari, and Amiga versions of M were taken over by Dr. T's Music Software. In 1994, Dr. T's stopped selling M, so the program has not been commercially available until EYES Co. Ltd. in Tokyo, Japan, contacted David Zicarelli in 1997 about reviving it, since they had a Japanese translation of the M manual and numerous customer requests for the program. EYES started selling M in September 1997.
There are several references if you want to learn more about theory and history of M. A recent book that everyone interested in electronic music and its history should read is Electric Sound by Joel Chadabe, one of the original authors of M and a pioneer of interactive composition. You can learn more about this book at the Electronic Music Foundation web site.
David Zicarelli wrote an article describing M and Jam Factory in Computer Music Journal when they were first published in 1987. There were also numerous magazine articles and reviews that cover M in Keyboard, Electronic Musician, Music Technology (UK), and Sound on Sound. Good luck finding them.