The thing is sponsored by R5 Productions, which is a local concert promoter.
http://www.r5productions.com/
They book small shows in the Philly area. Their main headquarters is in the First Unitarian Church. I'm on their mailing list.
When I saw Henry Rollins spoken word tour a few months ago, he actually performed in the altar area and we sat in pews. It was "The Church of Henry" that night. A month later, I saw High on Fire & Priestess in the basement of the church, where most shows are performed.
So yea, throughout the week, rock/punk/alternative concerts are performed there, then on Sundays, it's a fully functional church. The actual church is like 200 years old. It's a historical landmark in the city. I think Ben Franklin worshiped there or something.
_________________
A legend in posting since February 1st, 2007