Leroy Elliott Stewart got the nickname Slam from his forceful pizzicato attack, but the bowing-and-humming thing is what everyone remembers. He developed the technique in the 1930s, partly inspired by Stuff Smith, who used to hum along with his violin. Stewart applied the idea to the bass and pushed it further — not just humming in unison but consistently an octave above the bowed note, which gives the combination a warm, slightly surreal doubling effect. It's one of those ideas that sounds gimmicky when you describe it but is completely convincing when you actually hear it.

He came up in Englewood, New Jersey, and studied at the Boston Conservatory before making his name in New York. The big break came when he teamed up with guitarist Slim Gaillard in the late 1930s. The duo called themselves Slim and Slam, and they had an actual hit with "Flat Foot Floogie" in 1938 — a novelty record by most measures, but one with real musicianship underneath the silliness. Stewart was never just a novelty act, though. He was a serious swing bassist with a locked-in sense of time, and the comedy was more about Gaillard's personality than about Stewart's playing.

By the 1940s Stewart was working with Art Tatum, which tells you something about his caliber. Tatum didn't suffer mediocre rhythm players lightly, and the two had a genuine rapport. Stewart also recorded and performed with Benny Goodman and appeared on sessions that put him squarely in the mainstream of swing-era jazz. When bebop arrived he wasn't left behind — he played with Dizzy Gillespie and Charlie Parker on early recordings, and while he wasn't primarily a bop bassist, he could hold his own in that company.

What's easy to miss if you only know the humming trick is how clean and rhythmically solid his pizzicato playing was. He walked a bass line with authority, kept the pulse steady without being mechanical, and had good ears for harmony. The technique was a signature, but the musicianship underneath it was the real reason people kept calling him for sessions across four decades. You can hear a version of Slim and Slam: The Chronological Slim Gaillard (1938-1939) that captures how loose and fun those early recordings were, while still showing what a capable musician Stewart was even in that context.

He kept working well into the 1970s and 1980s, teaching at Binghamton University and continuing to gig. He wasn't chasing trends or reinventing himself — he was a guy who had a sound he believed in and stuck with it. That kind of consistency gets underrated. There's a directness to his playing that holds up; put on almost anything he recorded with Tatum and you'll hear two musicians who understood exactly what they were doing together.