On Windows 10 x64, I've been getting a bug where the frequency passed from onUserSoundSample is a lower frequency I expect.
In order to reproduce this, the following should create a constant, 440hz sine wave for the first 127 seconds from the start. Afterwards, the pitch should lower:
virtual float onUserSoundSample(int nChannel, float fGlobalTime, float fTimeStep) {
return sinf(440.0f * 2.0f * 3.14159f * fGlobalTime);
}