The punchline was all that I hoped for. You definitely topped yourself with this one. This is even better than Call Me in the Morning. I don't know what is funnier: Snape's uncontrollable laughter, their awful performance or the fact that Colin and Ron seemed to hook up in the end.
Either way, if there was ever a Harry Potter Humor Fanfiction Hall of Fame, this story would be one of the inductees. I am still chuckling after reading this.
While their band was a disaster, at least Ron can take solace in the fact that he got Gryffindor 200 house points.