The Soul Giants
From Zappa Wiki Jawaka
In the early 60's, Roy Estrada and Dave Coronado formed a band called the Viscounts. When their drummer quit, Roy bumped into Jimmy Carl Black in a local music store and Black immediately offered his services as a drummer. The band soon changed its name to the Soul Giants. When the Soul Giants auditioned at a newly opened club in Inglewood called The Broadside, the club owner told them that they would get the job if they would take Ray Collins as a singer (Collins had been working as a carpenter at The Broadside at the time). The Soul Giants added Ray, who eventually replaced their singer and the line-up was thus: Roy Estrada - bass / Jimmy Carl Black - drums / Ray Collins - vocals / Dave Coronado - saxophone / Ray Hunt - guitar.
When Hunt left the band, Collins contacted his acquaintance from Pal Studios Frank Zappa. Black: "Frank came down and tried out with the band and he liked what we did, and we liked what he did, so he joined. A month later the saxophone player Davey Coronado left the band, leaving the position of leadership wide open. Frank took over as leader, and his very words were, "If you will play my music, I will make you rich and famous."
According to FZ, the band changed it's name to The Mothers on Mother's Day, 5/10/1964; however, by all accounts, FZ joined the Soul Giants after his arrest on pornography charges on 3/26/1965. Unless Frank was referring to "the Muthers" power trio (with Les Papp and Paul Woods), which is unlikely, this is the first minor (?) descrepancy in the documented history of The Mothers.