Wow! I didn't even think that level creation was done automatically. That's really cool.
Thanks! These emails are actually me hitting drums on the midi recording. Basically, Godot Midi plugin allows to listen to note on/off events, and the rest of it is just a matter of spawning something on the correct track with correct timing.
I tried to use ones from the music file first, and it even worked, but was insanely hard to play, needed to simplify.