Character information for Western music can be input through the Apple Character Palette. Western music is included in ISO-IEC 10646-Universal Character Set. The proposal was submitted by Perry Roland of the Library of the University of Virginia which is also home to the Music Encoding Initiative (MEI).
There are some glyphs for Western music in the Apple Symbol font. Setting sheet music may be another matter. In part a richer font would be needed, and in part a richer positioning system than a plain typographic one would be needed. Perhaps if you want more than a symbol or two inserted in a line of type, the Music Encoding Initiative may provide a start?
/hh
Reference:
http://www.lib.virginia.edu/digital/resndev/mei/