This project was born after having a piano that was always slightly out of tune, so if I tried playing along with YouTube videos, it would sound like garbage. I figured if I could speed up or slow down videos the correct amount, I'd be able to tune the video to match the piano, instead of getting the piano tuned (which can be expensive). This extension may not provide the ideal approach, but hey, it's free!
Note: a lot of this code was copied from other extensions and slightly modified to get the instrument tuning bit