Jemmott began playing the acoustic bass when he discovered Paul Chambers at age 10. Jemmott began his career at age 12, and after switching to the electric bass, was discovered by saxophonist King Curtis in 1966. With his connection through Curtis to Atlantic Records, Jemmott soon began recording with other Atlantic recording artists, including Aretha Franklin, Ray Charles, Wilson Pickett, The Rascals, Roberta Flack and Margie Joseph. Jemmott also recorded with noted blues artists B.B. King, Freddie King, Chuck Berry, Duane Allman, Otis Rush, Champion Jack Dupree, and backed jazz artists Herbie Hancock, Freddie Hubbard, Erroll Garner, Les McCann, Eddie Harris, Houston Person, George Benson, Archie Shepp, Lionel Hampton, Herbie Mann, Eddie Palmieri and Charles Earland. He played the bass line for the original recording of Mr. Bojangles, and contributed to B.B. King's The Thrill Is Gone.