They have a demo available. store.steampowered.com/app/…/Dead_as_Disco/

From what I played, the attack matches the music automatically, and you do not need to worry about pressing buttons on the beat.

You can attack with no concern about timing (mashing, for example), and the animation will always hit to complement the music. Like, if the music has a quick ta-ta-ta, pressing the attack will show your character quickly punching 3 times matching it.