Not sure about map function...
If you want to use variable playback rate using memory, you would need to slightly alter the source code, play_serialflash_raw.cpp in the audio library. Or better, copy the .h and .cpp...
Awesome, Im really glad to hear that!
There is still a little bit of work required - when playing in reverse and the pointer reaches zero, it currently freezes. It should be fairly easy to fix, just haven't had much...