How hard is put new songs in this engine?

[Elmisteriosoytz]

I want to use the base of this engine to make a rasonable rythim game, beacause I only make a simple ryth where the notes appear randomly, and I want to make them go with the song and I want to know how much hard is to do here.

[WarlyFarly-Github]

I think when you build the game there's a bundles folder where you put songs in.