Bands who completely changed their sound...

[CanuckAmok]

Right off the bat, I'm thinking Roxy Music (I'm listening to their first LP right now, and can't imagine them doing "Avalon", and Jefferson Aeroplane/Starship...

who else did an aural 180?

[JuniperLea]

1. ew!

Metallica... Aerosmith... Korn... the newer stuf sux!

But when you think about it, so did The Beatles and they did ok.

[LoZoccolo]

2. U2

And I actually liked their weird Achtung Baby period better.

[NewHampshireDem]

10. They were the first ones to come to my mind ...

I'm glad they've gone back (well, at least a little ways back) to their roots. It's funny ... have you noticed that "Beautful Day" is actually a very, very different song when you play it full blast than when you play it at a more moderate volume?

BTW, if you're a U2 fan, buy the "U2 Go Home" DVD ... it absolutely rocks. (It's the inspiration of my observation above.)

[Ruffhowse]

3. Neil Young....

....has been a musical chameleon just about forever. I've got some albums by him that are incredible departures from his more well known stuff.

[guitar man]

4. The Doobie Brothers

Huge change when Michael McDonald joined up.

[Torgo]

5. King Crimson

Although they were always progressive and jazzy-sounding, I think that the period with Fripp and Beaulieu was their best. They sounded very different from earlier periods.

[ProfessorGAC]

17. Good Catch

Adrian's last name is spelled Belew, though. Sorry to nitpick, but that era of Crimson is among my favorite bands of all time. He even once, in an interview, disputed that his family name was ever spelled in the French style.

But, we agree that the shift from Court of the Crimson King to Beat was a remarkable one.
The Professor

[JaySherman]

6. Pantera.

Started out as a glam band.

http://www.kanged.com/pantera/pantglam.asp

[vi5]

7. Uh....Radiohead?

The come to mind first.

[Atlas Mugged]

8. The Jesus & Mary Chain

And who can forget Spinal Taps detour into jazz fusion?

[BigMcLargehuge]

14. Tap Lines!

Free form jazz explosion

[Screaming Lord Byron]

9. Mercury Rev and the Flaming Lips.

Kinda.

[NewHampshireDem]

11. Beastie Boys

They've been all over the map within their genre.

[name not needed]

12. Metallica

[BigMcLargehuge]

13. OMD

they went from ersatz Kraftwerk to ersatz Simple Minds

[Screaming Lord Byron]

15. and it wasn't a good step.

[Richardo]

16. Fleetwood Mac

Contrast "Oh Well" to anything from the Nicks/Buckingham era.

[XNASA]

18. Ministry

I would be remiss, if I did not mention them. ;-)

[eyesroll]

22. I used to sing along with "Halloween" on the school bus...

imagine my surprise, years later...

[XNASA]

19. Forgot XTC

How does a band get from "X Wires" to "Easter Theater"?

[Khephra]

20. Anthrax

[Mike Daniels]

21. Genesis

Went from menacing 10 minute long songs about killer plants, hermaphrodites and gang warfare to bland pop love songs.

[Beware the Beast Man]

23. Corrosion of Conformity

Went from hardcore/thrash to speed metal to southern rock over the years. Still a great band, though.

EDIT: here's others:

1. Ministry- Industrial/synth pop to Metal
2. Radiohead- guitar-based, U2 and Smiths-influenced rock to electronic music
3. Black Flag- Hardcore to Metal/Rock/Jazz fusion
4. Goo Goo Dolls- power pop/punk to bleeding sellouts

[tcfrogs]

24. R.E.M.

[mitchum]

25. Joy Division into New Order