At the time of his studies, he had begun a singing career as a guest vocalist for the jazz bands of percussionist Armando Peraza, saxophonist Jimmy Forrest, and guitarist Grant Green.
During the late 90's, Thomas toured the US and Europe with a band named Blueswing, led by Music Director/Guitarist Kevin McNeal, Billy Kaye on Drums, Ian McDonald/piano and Hilliard Greene/stick double bass.
"[5] Thomas's extension of the anthropological "verbal energy"—"whenever his Pygmy-yodel-scat erupted from the opening at the top of his larynx"—returns the listener back to "Pygmy yodeling not only via ethnomusicological investigation but via ur-soul, or back-to-Africa spiritual pilgrimage", Plantenga said.
[6] According to Ben Ratliff of The New York Times, Thomas had begun his career "as a straight blues-jazz singer" with a "stout tenor voice", but by the mid-1960s, he "had begun to spend time with young jazz musicians who were looking to Africa, the East and meditation for musical material … Thomas developed his ululating singing style, which has been compared to African pygmy and American Indian singing techniques and which he later called 'soularphone.'
But that's just the beginning, for despite the generation lag, Thomas beats Turner and Williams in their mode even while singing his own, and he turns scatting from a virtuoso trick into an atavistic call from the unconscious.
[7]AllMusic critic Thom Jurek, impressed especially by The Leon Thomas Album (1970), was mystified by "why this guy wasn't huge",[8] while Tom Hull said, "In a simpler time, he would have been a classic blues shouter.