I'm using a music speed changer to slow down given music to determine the exact the notes used so I can play the same notes (by ear) on my instrument of choice.
If this were a traditional tape or record player, slowing down the play speed would also lower the frequency (pitch) of the notes played. Effectively transposing the audio to a lower key.
To prevent this, the music speed changer will alter the track, cutting and pasting tiny sections of sound to extend them, so that the pitch does not need to be lowered. (by frequency stretching) Unfortunately, when the program does this, there are uncomfortable clicking sounds, especially where there is a lot of natural vibrato.
At times, I want to hear undistorted sound, and just tolerate the lower pitch.
If I set play speed to 50% then the octave change is naturally -1.
If I choose octave change of -0.5, then play speed needs to be roughly 70% to match.
How can I calculate the exact play speed needed to match the an arbitrary octave/pitch change? There has to be a simple
log base 2 function I can use, but I don't see how to make it work.