Thomas studied music at Tennessee State University. In the 1960s he was a vocalist for Count Basie and others.In 1969, he released his first solo album for the prestigious Flying Dutchman label. However he made an earlier album that is still unreleased even now.He was largely forgotten until a resurgence of interest in soul jazz. Several of his tracks have been sampled in hip-hop and downtempo records.He changed his name to Leone in 1974 because of an interest he had in numerology at the time. He did not legally change his name and he reverted to Leon shortly thereafter.Thomas is best known for his work with Pharoah Sanders, particularly the 1969 song "The Creator Has a Master Plan" from Sanders' Karma
album. Thomas's most distinctive device was that he often broke out into yodeling in the middle of a vocal. This style has influenced singers James Moody, Tim Buckley and Bobby McFerrin, among others. He said in an interview that he developed this style after he fell and broke his teeth before an important show.Thomas toured and recorded as a member of the band Santana in 1973.Thomas died of heart failure on May 8, 1999.