Very fast sine wave generator (2 PowerPC instructions per output sample!) implemented using a ringing filter. This generates a much cleaner sine wave than a table lookup oscillator and is a lot faster. However, the amplitude of the wave will vary with frequency. Generally the amplitude will go down as you raise the frequency and go up as you lower the frequency.
Frequency in Hertz.
Initial phase offset.
Output will be multiplied by this value.
This value will be added to the output.