Jazz is freestyle music. At it's best, the muse is just flowing through you. At worst, can be cacophonous. But when done right, it can still sound melodic if the players have a good rapport.
This seems to be what Wii Music is trying to encourage, and also why musicians seem to like this more than rhythm games.
A flashy-first game is awesome when it comes out. A great-first game is awesome forever.
Plus, just for the hell of it: Kelly Brook at the 2008 BAFTAs








