No idea about the chips themselves, but you can alter the speed of playback in software, its how all the Arduino wavetable and frequency on frequency synths work.
I assume the samples are stored as 8-bit numbers, to change the playback speed, you just need to step through the samples at a different rate than the original sample rate.
This project plays back wavetables at different rates to create the music you hear using the same idea -
Duane B.