Thanks for all the replies. SmarterThanSam I saw the midi definitions in mmsystem.h too. I also see wave pitch control, WAVECAPS_PITCH. Is this usable? Sorry I'm new to C++. There's two functions that look interesting.
MMRESULT WINAPI waveOutSetPitch(HWAVEOUT hwo, DWORD dwPitch);
MMRESULT WINAPI waveOutSetPlaybackRate(HWAVEOUT hwo, DWORD dwRate);