I have several multi-track piece of CDLC, but they basically go ignored. Typically my guitar is set slightly louder than the song to begin with, but it's nice to be able to hear the track in-game in case there's something I need to listen and make sure I'm playing correctly. Beyond that, I play in multiplayer a lot, and missing a correct backing audio for a song is a great way to make sure my friends who don't already know the song are going to be completely lost haha.