The show's producers announced Sunday that Armstrong will take over the role of persuasive drug dealer St. Jimmy for eight performances from Tuesday through Oct. 3. before leaving town to kick off his band's South American tour.
It's the Broadway debut for Armstrong, who composed and co-wrote the musical.
Armstrong temporarily replaces actor Tony Vincent, who's on leave until Oct. 12 for what producers call a personal family matter.
The show follows an antihero who flees a deadening suburbia and descends into sex, drugs and fierce guitar playing in his quest to find himself in the big city.
