I haven't tried this, so I don't know how convincing it'll be, but perhaps just raising the pitch will work OK? If so, you can do that with the BASS_FX add-on's tempo processing. You could try playing one of your recordings with the pre-compiled TEMPO.EXE example included in the BASS_FX package (C\BIN folder) and adjusting the "Pitch Scaling" option to see if it'll work for you.
