Rock stars have been talking trash about each other for as long as they’ve been making music (while there may not be any evidence to support this, we bet Beethoven had some not-so-nice things to say about Mozart). And while some musicians may not be as eloquent with their words as they are with their chord progressions, what they lack in rhetoric they more than make up for with bitchiness. We count down the harshest musician-on-musician insults of all time.