by Steve HueyBest-known as the late Stevie Ray Vaughan's rock-solid rhythm section, Double Trouble actually began life as a band of equals in 1978, the year vocalist Lou Ann Barton left a blues group called Triple Threat in which Vaughan was the guitarist. Accompanied by bassist Jackie Newhouse and drummer Chris "Whipper" Layton, Vaughan took over vocal duties and the band renamed itself Double Trouble after an Otis Rush song. Bassist Tommy Shannon, who learned the blues serving an apprenticeship with Johnny Winter, joined the outfit in 1980, and he and Layton would accompany Vaughan throughout the guitarist's meteoric career, from his 1983 debut album Texas Flood to his tragic death in 1990. Shannon and Layton regrouped as part of a blues-rock supergroup called the Arc Angels, who released a self-titled album in 1992; subsequently, the duo became an in-demand session team, backing artists like W.C. Clark, Kenny Wayne Shepherd, and Doyle Bram...