From what I've found online so far, it seems as though the Spotify SDK does not allow developers to manipulate audio (by slowing down songs/changing their pitch); all it allows you to do is simply play the audio at its original pitch/speed.
What I'm wondering is how apps like the Amazing Slow Downer (https://apps.apple.com/us/app/amazing-slow-downer/id308998718) are able to manipulate audio pitch/tempo from Spotify/Apple Music?
I am trying to accomplish this for an iOS app I am building, but I have no idea where to start -- I would appreciate any help in pointing me in the right direction to learn how I can do this!