1. Bee Gees - From Psuedo Beatles to Disco Kings

2. Beatles - From the greatest pop band of the early-mid 60's to a somewhat Psychedelic band

3. Miles Davis - From Acoustic Bop & Cool to Heavy Avante Garde Fusion

5. Kinks & Who (Tie) from popish mid 60's hard rock to very much late 60's & early 70's hard rock

4. (honorable mention) Prince - From Genius to Mediocrity

Well, Pink Floyd are out due to having lost Syd and Gained Dave....

Jeff Beck - from 60's rock guitar hero to 70's jazz fusion practitioner (not really a band...but you get the idea).

Too tired to think of anything else.

chicago - rock/jazz fusion with great writing and playing.......... to soft rock ballad hit machine

van morrison - wonderful singer/songwriter with provocative lyrics and interesting hooks.........to half-singing, half-talking bland songwriting junk

Spinal Tap/The Folksmen

Ministry: from catchy synthpop to grinding industrial

Genesis from Experimental Prog to Pop with Prog moments

Jethro Tull from Blues to Prog/Folk/Hard Rock

Fleetwood Mac from pure Blues to Adult Contemporary Rock gods

Journey from Jazz Fusion to AOR/Pop Rock (lord I hate that term)

Manfred Mann/Manfred Mann Chapter II/Manfred Mann's Earth Band (can't get any more different that these factions)

Jefferson Airplane/Jefferson Starship/Starship (seriously?)

When I first saw the thread title, I took the literal meaning ie bands splitting up to different bands that had same members.
Jefferson Airplane becoming Jefferson Starship (Kantner Slick Balin) and Hot Tuna (Jorma Jack).

As to the thread........

Grateful Dead - trippy psychedelic -> country rock influenced -> jam band (hate the term)

Bob Dylan - too many to mention

The Moody Blues - r&b British invasion -> prog/psychedelic
I prefer the first Denny Laine era.

You're the first person other then myself I've heard criticize VM's work of the last 30 years or so, but I agree. And you're spot on with Chicago also.

I did mean the same members, though I already broke the "rules" by mentioning Prince!

Speaking of which, under different band members both Neil Young & Bowie belong here too.

Fleetwood Mac Great Blues Band To pop Rock Band

Little Richard- great rocker to gospel singer to great rocker to gospel singer to great rocker......

not too many of these bands kept the same members so

I'd go with Little Feat started as a more guitar driven band to the funkier 6 piece band.

if you include solo artists (with band sometimes) - no one had done more changes than Frank Zappa.

also Captain Beefheart's Magic Band - big change from Safe As Milk to all else that came after.

here's one that tried to change

Paul Revere & the Raiders - from a "hit singles" driven band to their last releases of the 60's where they tried to move into the FM type band - I think they even tried a "Ruben & the Jets" type move - released an lp under an assumed name to try to get FM radio play.

the police from ska/reggae/punk on their first album to rock/fusion/prog on "synchronicity"

hall & oates from philly soul to pop/rock hit machine to philly soul

linda ronstadt - from country rock to pop/rock to big band to latin to soft/rock to alt country to .....and round and round we go.

Speaking of PR&TR There was the Monkee's "Head" & DC5 covering Neil Young's Southern Man........

This question made me think about bands who had gone through dramatic stylistic changes and yet somehow retained a sense of a core identity. For instance:

The Clash each album somewhat different than the one before but certain elements--including a degree of crazy abandon--hold it all together from album to album.

The Velvet Underground - Radically different from one album to the next but Lou Reed's songwriting (and his laconic voice) and Moe Tucker's drumming (except on the last album) make everything feel "of a whole."

I would argue that the Police also fall under this category--as different as Syncronicity is from the first album, for instance, it still has reggae touches and is obviously by the same band.

As far as a band that almost became unrecognizable even though they had the same members? How about Gang of Four? That's a very radical change. And possibly the KINGS of this category would be THE STRANGLERS--from hard edged brutish punk rock to sophisticated europop, all performed by the same four people.

I've argued before that the Beach Boys matured from a clean-cut, boys-next-door pop group to a scruffy, bona fide rock group by the early 70s.

I guess I'm misunderstanding the question posed by this thread--we're talking about bands whose music evolved so radically that it virtually leaped into an entirely different sort of musical genre?

That was my original intent, other than my smart assed comment about Prince.

I'd add these two to the list:

Los Lobos (mostly Spanish language traditional Mexican style to more of a Latin, arty rock sound)
ZZ Top (early blues rock to more synthesized pop rock)

XTC - Angular post-punk to pastoral power pop
Elvis & The Attractions - New Wave to R&B Revivalism to Country-Rock to Art-pop and back and around again

Whitesnake technically doesn't count because of many shuffled members, but they went from blues to hair metal.