ZZ Top has had to pull out of a headline appearance at Musikfest in Bethlehm, PA on August 1 and five other dates so bass player Dusty Hill has time to regain form after surgery this week to get a pair of kidney stones removed. The condition was discovered during a routine physical and Hill's MD recommended he get them out asap. The news deals a blow to the annual lineup on the Sands Steel Stage. The concert was approaching a sellout. ZZ Top plans to return to the road August 6 date in Sturgis, SD for an appearance that will open a series of dates that team Tres Hombres with guitar legend Jeff Beck.