Nearly ten years after they first were featured in this space, ZZ Top has, with the passing of bassist Dusty Hill, ended its tenure as the longest-running music group with an unchanged lineup. To call this the end of an era is an understatement, as would be any attempted summation of the band’s history and legacy. The trio consistently embodied the total rock and roll package, and today’s Jam is a small tribute of gratitude to their commitment, sound, and style: