RepeatingSound should have its own implementation which just passes on to its sound.
Maybe just replace
sound mixSampleCount: count into: aSoundBuffer startingAt: i leftVol: leftVol rightVol: rightVol.
with
sound mixSampleCount: count into: aSoundBuffer startingAt: i leftVol: leftVol * scaledVol rightVol: rightVol * scaledVol.
Hmmm...
Make it
sound mixSampleCount: count into: aSoundBuffer startingAt: i leftVol: leftVol * scaledVol // ScaleFactor rightVol: rightVol * scaledVol // ScaleFactor.
Stef