Bands that drastically changed musical styles

[kerze]

Bad Religion - from melodic hardcore on How Could Hell Be Any Wore to prog rock on Into the Unknown and then a break up and reunite for Suffer.

Joni Mitchell moved from folk to confessional pop music to experimental jazz.

I think the Beach Boys would also be a good example

Terence Trent D'Arby went from straight up R&B on Introducing the Hardline, to some fairly experimental stuff on Neither Fish Nor Flesh to alt-rock on Symphony or Damn and Vibrator.