We don’t often think of sidemen as comprising a “supergroup,” but there’s really no other way to describe Chicago’s Source One Band. Between them, bassist and bandleader Joe Pratt, lead guitarist Sir Walter Scott, keyboardist Stan Banks, and drummer Lewis “Big Lou” Powell have performed or recorded with a list of greats that starts with Koko Taylor, the Chi-Lites, the Jackson 5, Tyrone Davis, Otis Clay, Denise LaSalle, Johnnie Taylor, Artie “Blues Boy” White, Willie Clayton, and Latimore—and keeps going from there.