People who changed their role in bands

Over the years, a lot of personnel changes have taken place in bands.  One of the more interesting scenes is where a band member switches instruments or suddenly assumes a frontman position.  Most people have probably heard the story of Stewart Sutcliffe leaving The Beatles, and guitarist Paul McCartney drawing the short straw and having to become the bass player (which actually worked out pretty good!).  It's not the only time something like this has happened though....Roger Daltrey used to be the lead guitar player in a band called The Detours, but when frequent disagreements led to their vocalist leaving the band, Daltrey assumed the singing duties and became the frontman, handing off the guitar duties to rhythm guitar player Pete Townsend (another one of those situations where things worked out fine when they became The Who). There are other times where fate has led to people changing instruments too.....Tom Petty was originally a bass player who became a guitar player/singer with The Heartbreakers, Mickey Dolenz was the Monkees drummer and became a frontman singer/guitar player, Joe Butler went from being Lovin' Spoonful's drummer to frontman singer, and Dave Grohl went from being Nirvana's drummer to the singer/guitarist in Foo Fighters.

Any other unforeseen personnel changes in bands that you can think of?