Success getting TMRpcm to change the pitch and speed of sounds

Using Arduino Audio
5

I think this is how (assuming you're using a 16-bit timer):

unsigned long newSR = map(analogRead(A0), 0, 1023, 8000, 44100);

if (bitRead(optionByte,6)) *ICRn[tt] = 10 * (800000 /  newSR);
else *ICRn[tt] = 10 * (1600000 / newSR);

optionByte and ICRn are actually global variables, so there should be no problem in using them anywhere (at compiling time though); furthermore no library modification required.
Although not sure if there would be a side effect since this also changes PWM's (carrier) frequency, and if the duty cycle (outputted sample's value) will be scaled accordingly.