Famous musicians before they were famous - guest spots

What popular albums/singles can you name where a future famous musician was an unknown background player, etc.?
Examples,

On some of Barry Manilow's 1970's albums, I have seen both Paul Schaeffer and Will Lee listed as the musicians (both later part of David Letterman's band of course)

Marvin Gaye was part of the 1950's group the Moonglows, also I think he may have been a drummer on some of the early Motown songs

Daryl Hall was part of the Electric Indian, which had this hit instrumental song (he hates it but I think it's pretty catchy)

 

Tori Amos sung on Al Stewart's 1988 record, Last Days Of The Century & later co-wrote Charlotte Corday from 1993's Famous Last Words, which did, admittedly, appear a short while after Little Earthquakes came out.

Richard Page sung on a bunch of REO Speedwagon records before Mr Mister took off (despite their broken wings. Badoom Tish!).

 

The Captain (later of Captain and Tenille), Daryl Dragon, was deeply involved in Dennis Wilson's wonderful "Lady" single.

 

The backing band on P.J. Proby's "Three Week Hero" album is a yet-to-be-named Led Zeppelin.

 

Not sure if this counts, but...... a few of Fleetwood Mac's Peter Green-era albums credit Christine Perfect as a guest keyboard player - who, come 1971, would become FM's official keyboard player (now under her married name McVie)!

 

Carlos Santana wasn’t a complete unknown but was pre-fame when he stood in for Mike Bloomfield on what may be his recording debut with Al Kooper.

Sonny Boy Williamson

 

Though his first album had already been released, Joe Satriani hadn't really taken off when he appeared on the first Crowded House album. Oddly enough, it's as a backing vocalist.

 

Flea of RHCP on Young MC's Bust a Move (1988). It's a great bassline but he only got paid a fee, for shame!

 

Lowell George, Adrian Belew, and others, starting out being on Frank Zappa albums?

 

Dr John was initially a session guitarist with Ace records. He played on Sam Cooke's final recordings and, later, on Zappa's Freak Out!.

 

Chris had become a household name in the UK due to her work with Chicken Shack (label mates of FM), and had even won some 'favorite' contest in UK mags before she started working with FM

 

Huey Lewis - harmonica on Thin Lizzy: Live and Dangerous.

 

Kesha sang the chorus on Flo Rida's "Right Round" eight months before her debut single "Tik Tok" was released.

 

Martin Fry (ABC vocalist) played tuba on some tracks from Murray Head's Nigel Lived album. Yes, you read that right.

 

Tony Iommi:

 

Keb’ Mo’

Backed Papa John Creach as Kevin Moore in the early ‘70s. I saw this lineup perform.

No More Country Girls

 

Reg Dwight, better known as Elton John, played as a session musician on a ton of recordings before he became famous as a solo artist. The piano you hear on the Hollies' "He Ain't Heavy" is Reg.

 

10cc (all of them) did time as session musicians for the bubblegum label Buddah Records. The song "Sausalito" by the Ohio Express actually features all four of them.

 

Steven Tyler of Aerosmith sang on some Left Banke recording sessions in the 60s.

 

Bob Dylan playing harmonica on Caroyln Hesters s/t third album.

Led to him getting signed by John Hammond to Columbia Records.

 

Timothy B. Schmidt was a BG vocalist on Pretzel Logic, even before he was an Eagle.

 

Bob first appeared on Harry Belafonte Midnight Special LP.

 

How about Testify by the Isley Brothers featuring the Voodoo Child himself on guitar.

 

Frank Zappa from 1963, hilarious.

 

such as Fingertips