When I'm playing Rock Band 3 by myself, I want to go into Quickplay and sort the songs by their difficulty in Pro Keys. I can't figure out how-- when I log in from the keyboard and choose "Song Difficulty" as the sort order, it uses the regular Keys difficulty until I've played a song in Pro Keys.

Is there a way to choose Pro Keys from the song sort/filter menu, and I just don't see it? Is there some other solution?

(I'm on Xbox, if that matters, and this is the keyboard controller that came in the game/keys bundle.)