Look for information about mod/s3m/etc. trackers and players. hornet.org had a lot of good stuff before it was shut down, dunno if its still up(I mirrored and have it all CD .

The basic idea is this: You say that playing the sample at 11kHz produces C-3. Well, since the frequency and sampling rate are very coupled, you just adjust the playback rate(speed it up or slow it down). Well there are twelve notes in an octave, and a octave difference is twice the frequency. Treat sampling rate as the "frequency", note this makes C-4 22kHz. The way to figure any note involves a geometric series that doubles every 12 steps. You end up with the twelfth root of 2 as a constant, I think its like basefreq * (const ^ (note number)). Thats not exactly right, but thats the idea.