Lord Zedd | Rock Band Blitz - Offline Unlock Mod (ft. Spooky Scary Skeletons) @Zeddikins | Uploaded 9 years ago | Updated 33 seconds ago
So I managed to get the game working offline with powerups, only downside is scores/controls don't save.
"Spooky Scary Skeletons" is by Andrew Gold, and was charted by BearzUnlimited from C3.

Grab the xex here: http://www.mediafire.com/download/1m8gq90gefvx2m1/blitz_defaultunlock.rar