The area of the Lower East Side known as Hells Square is undergoing a lot of change, but hey, Max Fish is reopening tomorrow and we’re told Lady Gaga has been hanging out at the new incarnation of her old haunt St. Jerome’s, which recently opened a back room and added a food menu. The video above, taken by Nicky Digital, shows Gaga, after appearing with Tony Bennett at Lincoln Center this past Monday, dropping into Rivington F&B to sing Nancy Sinatra’s “Bang Bang.”

We hear that only about 100 people caught her impromptu performance with jazzman Brian Newman at the bar’s Magic Mondays party, which featured seven songs including a duet with Tommy London from Dirty Pearls, and a striptease by Angie Pontani.

Jonas Pelli, a former bartender and manager at St. Jerome’s, opened Rivington F&B back in March along with fellow first-time operator Omri S. Quire and Paul Seres of The DL. About a month ago, they opened a back room with a cocktail list by Shane Tison of The Randolph at Broome and a grilled cheese menu featuring “The Ultragrrrld” (oh-so-cleverly named after downtown music writer/producer/tastemaker Ultragrrrl). That along with the art by Dead Flowers NYC (known for skeleton-izing iconic photos of rockers) is an indicator of what they’re going for: a rock bar along the lines of bygone Motor City.

You can find photos from Gaga’s here and here, and here are some photos of the new back room sans Gaga.