[CM] Enabling Common Music in S7

[bil at ccrma.Stanford.EDU]

Grace's scheme files are in Resources/Scheme, I think.  It won't
hurt anything to load stuff.scm and r7rs.scm, but I'd recommend
simply extracting the functions you need.  reactive.scm is more
a test of setters -- if you want to try reactive programming,
it's something to look at.  I don't like this style of work
because it hides all the set!'s -- I wouldn't want to debug
such code!