What are Ben Affleck and Jennifer Lopez doing five or sometimes even six times a week? Sometimes with Liv Tyler as well?

The Jersey Girl stars are working out with Lopez’s personal trainer, Gunnar Peterson, who flew in from Beverly Hills last month for the film shoot. Peterson, who also trains Christian Slater, Penelope Cruz, Sylvester Stallone and others, found discreet local gyms. He says the actors – “in great shape in every way” – do 60 to 90 minutes of weights, interval training, “super setting” (two exercises back-to-back before resting), and “peripheral heart action.”

They love it. “Exercise doesn’t have to be that foreboding thing that hangs out there that we all dread,” Peterson says. “They come in happy, they laugh, we get it done.” Longest he’s been out of his studio was four months, when he trained Mike Tyson. “I called my wife [in California] the other day and said: ‘I’m a Philly guy now.’ ”

Sure. The one with the rock-hard abs.

Settlement Music School got a call late Sept. 13 – the Friday night of a three-day weekend – for an 18-piece adult orchestra for Tuesday morning. Settlement’s Bill Hughes managed to pull together faculty, who wore concert black and sat on stage at the Forrest Theater while Jersey Girl cameras filmed a scene from Sweeney Todd. Ben Affleck and young costar Raquel Castro watched from the balcony. The players played… not a note. Singers in the scene were miked, but music will be dubbed in later. “They wanted to make it look authentic,” says violinist Monique Johnson, surmising why she and fellow musicians put in an 11-hour day.