Unlocks the full soundtrack at the jukebox (or mini jukebox), including Sam’s alternate band songs, arcade game tracks, 14-heart remixes of songs, etc.
That only allows you to hear songs that you've heard in-game in the particular file you're playing. What I'm suggesting is a Qi Gem item that unlocks any tracks you haven't heard, including ones you'd never hear normally (such as Sam's other band song styles).