The math in A Geometry of Music is really fairly simple, using 3D geometry to demonstrate the relationships between pitches in harmony. I’d say it’s more music than math for the most part. Useful for composition, including algorithmic composition
Musimathics, Volume I and II puts more emphasis on signal math. Useful for DSP.
I also have a couple of books waiting in the wings when I’m done with those three. These books are about analyzing musical styles and using them to generate new works.
And there is a section titled Evolutionary Music in Creative Evolutionary Systems that I hope will be useful for generative composition as well.
I wish I read much faster than I do!