Appearing as part of a promotion for an international beer company, the full BSS lineup -- recently seen here at the 2010 Pitchfork festival -- played atop a 30-foot-high stage erected directly in front of one of the beer's billboards. The event took place in a parking lot near Addison and Sheffield, south across the street from Wrigley Field. (BSS tour mates TV on the Radio did this same promotional gig last month in New York.)

It's the ultimate hipster crisis of conscience: corporate sponsorship of indie rock kinda sucks ... but, hey, free show!

The last-minute mini-concert was promoted via a social media blitz, announced via Twitter early Wednesday several hours before showtime. Police on site estimated the resulting crowd around 700.

Chicago superfan Abigail Szymonik, who's seven months pregnant, said she read news of the show that afternoon on Facebook and didn't believe it. But she drove down Addison, anyway, and jumped out when she saw the crowd. "I'm sure I'm parked so wrong," she said, "but I just don't care!"

The band got late notice, too. "We just got this offer two weeks ago," said singer Kevin Drew, before extolling the virtues of their city of choice for the event. "Chicago, we love you. You know we do, and that's why we're here."

BSS recorded "Forgiveness Rock Record" at Soma in Chicago and produced by John McEntire (Tortoise, the Sea & Cake).

BSS made a professional, seamless run through seven songs, opening with the long groove of "Cause = Time" and the feisty "Texico Bitches." Drew seemed to work extra hard to maintain his energy, and Lisa Lobsinger sleepwalked through "Anthems for a 17-Year-Old Girl." Drew tried drumming up the crowd during "Ibi Dreams of Pavement," employing ye olde "everybody scream as loud as you can" trick, and then didn't seem to mind much when it wasn't very loud. They indeed looked like a band that deserves a year or three off.

Broken Social Scene : The Heineken billboard. from John Yingling @ GONZO CHICAGO on Vimeo.