CAMBRIDGE - Al Kooper, decked out in dark shades, was joking, but there was a hint of truth in his teasing.
The show could run until midnight, he said, "but they are selling Depends in the lobby."
Ba-dum-bum. Kooper was referring to Club Passim's 50th Anniversary Hoot (as in, an old-fashioned hootenanny) Sunday at the Brattle Theatre, and his humor was pointed, of course, to the graying hair in the audience as much as it was about the show's seven-hour duration.
A little after 4 p.m., Kooper, playing the day's only electric guitar, kicked off the marathon concert, which marked, to the very date, the historic opening of Club 47 on Mt. Auburn Street, now known as the Passim Center in the heart of Harvard Square.
As with any 50th anniversary, some of the leading lights have passed away: Eric von Schmidt, Richard and Mimi Fariña, Joe Val, Tim Hardin, Mel Lyman, Bill Woods, and so on. Others - Maria Muldaur, Bill Staines, Bonnie Raitt, and Joan Baez (who plays an anniversary concert at Sanders Theatre in March) - simply couldn't make it.
With such a watershed occasion, the Hoot's performers and audience were understandably ready to stroll down memory lane. It was an evening of shared memories, and everyone had a story to tell, starting with the guy next to me who recalled dating Mimi Fariña when she was still Mimi Baez and how Joan Baez and Bob Dylan drove each other crazy when they lived together because he was always stoned or drunk out of his mind.
Jim Kweskin, reunited with his fellow jug band cohort Geoff Muldaur, remembered taking a trip to Martha's Vineyard with then-girlfriend Paula Kelley, who co-owned Club 47 back then, and meeting up with Carolyn Hester and Richard Fariña.
And Bob Jones remembered everyone and everything. He used to run the hootenannies at Club 47 in both its locations, and he tapped his supreme knowledge of the 1960s folk scene as the evening's emcee.
Meanwhile Hester, whose pristine soprano is shockingly undiminished, was in a reflective mood, too. She sang a salute to Jacqueline Kennedy Onassis ("The Little Girl Who Saved America") and wondered, "Did anyone do 'Pack Up Your Sorrows' yet? Well, don't you think we oughta?"
John Nagy was particularly nostalgic and visibly moved to be playing again. He reminisced about a harrowing night at Cafe Yana, a folk venue that predated Club 47, during which his beloved banjo and 12-string guitar amazingly survived unscratched.