Arnold played in J. Floyd & the Shamrocks (who frequently featured a young James Brown on piano) while still in high school, and officially began his professional career when he joined Charles Miller’s band in the early '60s. He moved to Chicago around 1965 and began gigging with saxophonist A.C. Reed before hooking up with Muddy Waters and his band in 1966. The Waters stint led to a fair amount of studio work, and Arnold played bass on several 1960s blues albums, including Otis Spann’s The Blues Is Where It’s At and John Lee Hooker’s Live at Cafe Au Go Go.