Audio signal processing book suggestions
If you can get it:

Zölzer, Udo (1997). Digital Audio Signal Processing. John Wiley and Sons. ISBN 0-471-97226-6

or 

Orfanidis

might have to buy them used.

is your interest music processing and synthesis?

there are some nice online books.  Look for anything Julius Smith.  But there are others, but i can't remember any names to search for.

Remembered one:

Davide Rocchesso

here's another link

another old one:

Ken Steiglitz