[Brickcity]

Levon Helm, Richard Manuel The Band
Dr Hook
Meatloaf
Janis Joplin
Tina Turner
Ray Charles
James Brown
John Fogerty
Talking Heads
Stevie Nicks , Lindsey Buckingham Fleetwood Mac

Yes a bit bored but what the heck.  Anyone?  Anyone?

I know your question was more focused on the groups, but I'll focus on my favorite voices:

BB King
Aretha Franklin
Paul McCartney
Elton John

For great voices in the context of their music, though perhaps not as universally as appealing as ones above, I'd have to add...

Mick Jagger
Jim Morrison
Louis Armstrong
John Lennon

[Brickcity]

Levon Helm, Richard Manuel The Band
Dr Hook
Meatloaf
Janis Joplin
Tina Turner
Ray Charles
James Brown
John Fogerty
Talking Heads
Stevie Nicks , Lindsey Buckingham Fleetwood Mac

Yes a bit bored but what the heck.  Anyone?  Anyone?

I know your question was more focused on the groups, but I'll focus on my favorite voices:

BB King
Aretha Franklin
Paul McCartney
Elton John

For great voices in the context of their music, though perhaps not as universally as appealing as ones above, I'd have to add...

Mick Jagger
Jim Morrison
Louis Armstrong
John Lennon