Amos Leon Thomas Jr. (October 4, 1937 – May 8, 1999), known professionally as Leon Thomas, was an American jazz and blues vocalist, born in East St. Louis, Illinois, and known for his bellowing glottal-stopstyle of free jazz singing in the late 1960s and 1970s.

Leon Thomas was born Amos Thomas, Jr. on October 4, 1937, in East St. Louis, Illinois. He studied music at Tennessee State University. 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. His musical development at this time was shaped in part by seeing saxophonist John Coltrane perform in trumpeter Miles Davis‘s sextet during the late 1950s. Thomas moved to New York City in 1959, singing at the Apollo Theater as a vocalist for acts such as jazz ensemble The Jazz Messengersand singer Dakota Staton. In 1961, he joined the Count Basie Orchestra but soon left after being conscripted into the army.

Thomas was discharged from the army in the late 1960s and resumed his music career, first working with avant-garde jazz saxophonist Pharoah Sanders. In 1969, he released his first solo album for Bob Thiele‘s Flying Dutchman label. Thomas became best known for his work with 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. He said in an interview that he developed this style after he fell and broke his teeth before an important show. Some of the vocal style is classified as ‘jive singing’. (Ref: Leon Thomas Blues Band album).^{[citation needed]} Thomas saw music as a means of social commentary during this period, saying, “You just have to be more than an entertainer. How the blazes can you ignore what is happening?”