I want know if setting Engine.time_scale
changes how fast my music is being played
Engine.time_scale
controls how fast or slow the in-game clock ticks versus the real life one.
It does not affect the music/audio speed.
You can adjust the pitch scale of AudioStreamPlayers
to adjust playback speed.
Also if you'd like to speed up audio without changing it's pitch too much - you can try this out: https://godotengine.org/qa/88935/how-can-i-change-speed-of-an-audio-without-changing-its-pitch