Key background generator from audio?

I want to affect a background video from music dynamics, is there a simple way to do this? I've searched and can't find anything apart from making spectral stuff in motion. I'm making a simple lyric video and want the background to subtly change as the music dynamics change.
Appreciate any help or advice

Unless someone knows of a plugin that you can purchase, Motion is going to be the option for achieving what you're looking for. Nothing built into Final Cut can do what you're looking for.