This one's pretty good for audio DSP in general, including some fairly detailed material on synthesis:

https://mitpress.mit.edu/books/audio-programming-book

Most of the code is C (and some C++). The first two chapters are a C tutorial, followed by audio-specific C programming. If you already know C you may want to skip the first couple of chapters.

If you're going to buy it I'd recommend a hard copy, as the DVD includes a lot of stuff that isn't in the Kindle version.