When he was about 15 years old, McClain hooked up with Little Melvin Underwood, a blues guitarist from Mississippi.
"I started as his valet, and I worked my way up to backup singing. And then I worked my way up to lead vocal."
He traveled with Little Melvin's band until they stopped in Pensacola, Florida in 1963. "We went to Pensacola
for two days, and I stayed ten years!" He laughs. Little Melvin was headed north. "I said, 'I want to hang right
here, with the big palm trees and the beach!'" He laughs again. "So that's when I quit the band."
It was in Pensacola that McClain got his nickname. "Before I got there, I was called 'Good Rockin' Sam.' And
a club owner there, Tom Golson, somehow me made a mistake and put up 'Mighty Sam.' And it stuck. It's been Mighty ever since."
He kept busy in Pensacola, singing
at Tom's Tavern and Abe's 506 Club, and going on regional tours with the Dothan Sextet, a regional band that had once backed
up Otis Redding.
At one of his gigs, McClain caught the attention of Papa Don Schroeder,
a local DJ who was trying to get into the recording business. Papa Don arranged some recording sessions for him at Muscle
Shoals, Alabama; one of the tracks he cut was "Sweet Dreams," a country song made famous by Patsy Cline.
"Sweet Dreams" became a minor hit for McClain in 1966. He toured as a headliner, including a stop
at the renowned Apollo Theatre in New York City. "I went from standin' on the corner to making 1200, 1400, 1600 dollars
a week," he recalls. "But as soon as it happened, it was over. It was like God took me to the mountaintop, showed
me what I can have if I'm willing to work for it, and then it was all over. And there I was, from the Apollo Theatre, working
with Albert King, Jackie Wilson, and all those people, and the next thing I knew I was eatin' out of a garbage can."