I’ve already snuggled into my Audiogon winter hibernation, but this topic is just too irresistible to not participate in. In alpha order, including names perhaps unfamiliar to some:
- T Bone Burnett. His pre-solo group (with fellow members Steven Soles and David Mansfield) was named The Alpha Band (three albums).
- Peter Case. Originally a member of The Nerves (with Paul Collins---later of The Beat---and Jack Lee---writer of "Hanging On The Telephone"). His second band was The Plimsouls.
- Kasey Chambers. The fantastic Australian singer, originally a member (along with her mother, father, and brother) of The Dead Ringer Band.
- Eric Clapton. The Yardbirds, of course. He’s on the Five Live album, then about half the songs on the For Your Love album (with Jeff Beck on the others).
- Ry Cooder. Prior to getting his Warner Brothers deal, Ry was in The Rising Sons (with Taj Mahal and Ed Cassidy, the latter later in Spirit), then Captain Beefhearts Magic Band (first album only).
- Sam Cooke. Originally in the Gospel group The Soul Stirrers.
- Elvis Costello. From 1974-76 EC was in a Pub Rock group named Flip City.
- Marshall Crenshaw. Originally a member of the touring cast of Beatlemania.
- Rodney Crowell. Prior to embarking on his solo career, Rodney was a member of Emmylou Harris’ Hot Band, then a member of The Cherry Bombs (along with Vince Gill and Tony Brown, the latter later to become a very hot Nashville record producer).
- Dave Edmunds. Dave’s pre-solo group was Love Sculpture (one Blues album, one semi-Progressive---ala "Sabre Dance"). His 1970’s and 80’s albums are fantastic, as is the one album by his group with Nick Lowe, Rockpile.
- Robben Ford. Before moving to L.A. to eventually work with Joni Mitchell, Miles Davis, and George Harrison---as well as making a number of solo albums, Robben was in a Northern California band with his two brothers, The Charles Ford (their Dad) Band. I saw them live quite a few times.
- Vince Gill. Vince got his start as a member of The Pure Prairie League, then The Cherry Bombs (with fellow member Rodney Crowell).
- Debbie Harry. Deb began as a background singer in the hippie band Wind In The Willows (one album, undoubtedly terrible ;-) .
- John Hiatt. Before getting a solo deal, John was member of a group named White Duck (two albums on Uni Records, not very good imo).
- Waylon Jennings. Originally the bassist in Buddy Holly’s road band. Waylon gave up his seat on the plane that took Buddy’s life to The Big Bopper, who also went down in that Iowa corn field.
- Albert Lee. Prior to moving to America and working in the bands of Emmylou Harris and The Everly Brothers, and then later embarking on a solo career, this incredible guitarist was in the Welsh band Heads Hands & Feet.
- Darlene Love. One of the greatest voices of our lifetimes, Darlene was originally a member of The Blossoms.
- Nick Lowe. NIck started out in the UK Pub Band Brinsley Schwarz. His solo recordings made with the members of Rockpile (Dave Edmunds, Billy Bremner, and Terry Williams) are fantastic.
- Moon Martin (writer of "Bad Case Of Loving You" and "Cadillac Walk"). Pre-solo, Moon was a member of Southwind (two albums on Blue Thumb).
- Van Morrison. Them, of course. I saw Them live when Van was still in the group.
- Maria Muldaur. Originally in The Jim Kweskin Jug Band.
- Wilson Pickett. Originally in The Falcons.
- Robert Plant. Prior to Led Zeppelin, Robert (and John Bonham) were in Band Of Joy.
- Boz Scaggs. Originally the rhythm guitarist (only) in The Steve Miller Blues Band. I saw this line up once, pre first album (the Blues was dropped from the name).
- Phil Spector. Phil got his start as a member of The Teddy Bears. He wrote their hit single "To Know Him Is To Love Him".
- Chris Stapleton. Before going solo, Chris was a member of The Steeldrivers.
- Marty Stuart. Before going solo, Marty was already a show biz veteran, having joined Lester Flatt’s band at the age of 14! When Lester retired, Marty moved over to Johnny Cashes road band.
- Stevie Ray Vaughan. One of Stevie’s many pre-fame bands was named Triple Threat Revue, with the fantastic singer Lou Ann Barton (you NEED her excellent Jerry Wexler-produced album Old Enough).
Terry Williams. Before joining up with Dave Edmunds and Nick Lowe, this fantastic Rock ’n’ Roll drummer was in the Welsh band Man. After Rockpile Terry joined Dire Straits.
There are plenty of others, which is why the op’s statement that he couldn’t name any astounded me.