The Music II is a sound synthesis software for computer music. It is an updated version of The previous Music I, and as the latter belongs to the family of Music N.
Completed in 1958 by Max Mathews, the Music II did not show much change from the Music I. However, the few changes made were enough to make software more versatile and functional than its predecessor. First was increased the number of voices, resulting in a polyphonic instrument capable of generating four different voices. Also increased the number of synthesis algorithms can be implemented, allowing, therefore, a better diversification of timbre. The most interesting, perhaps, was the introduction of the wavetable, which gave the possibility to synthesize sounds much more complex than those achievable with the Music I. As for the programming continued to use the IBM 704 assembler. Only after completion of the work this machine was replaced with IBM 7090, a computer better performance. This led Mathews to develop the Music III.
For this topic I’ve read.
 Alex Di Nunzio, Genesi, sviluppo e diffusione del software Music N nella storia della composizione informatica, Thesis, Università di Bologna: D.A.M.S. Musica, 2010.