Vocal jazz is a dynamic genre where the human voice functions as an instrument, characterized by syncopated rhythms, improvisation, and distinctive techniques like scat singing, where vocalists imitate instrumental tones and rhythms. Its origins trace back to early 20th-century African-American field hollers, work songs, and spirituals, with Louis Armstrong becoming a pivotal figure in popularizing vocal jazz from the late 1920s, notably pioneering scat in his 1926 recording "Heebie Jeebies."

The genre flourished through the 1940s bop era with legendary singers such as Ella Fitzgerald, Sarah Vaughan, and Billie Holiday, and continued to evolve into the more relaxed cool jazz of the 1950s, featuring artists like Peggy Lee and Chet Baker. Vocal jazz is further defined by specific techniques including pitch bending, conversational phrasing, and mixed-register singing, typically accompanied by a rhythm section and drawing heavily from the Great American Songbook for its repertoire.