The current Four Bitchin’ Babes, from left: Christine Lavin, Sally Fingerett, Debi Smith and Deirdre Flint. (Terry Jordan)

If you have a favorite song about lost car keys — or microwave dinners, or menopause, or HMOs, or erectile dysfunction, or staycations, or vibrators, or the history of cheese — there’s a decent chance it was written by one of the Four Bitchin’ Babes, the long-running folk quartet that does its truth-telling with levity, candor and quirk.

How do they write all those songs? Turns out, there have been more than four Babes. Since forming in 1990, the group has had at least eleven individual members — and that doesn’t include any of the “guest Babes,” “touring Babes” or “man Babes” who sometimes collaborate with the group, according to mainstay Debi Smith, who joined in 1994. So then, two more questions: What does it take to get in this band? And what does it take to stay in?

“Humor,” Smith says. “We all see things through a wacky viewfinder. We’re all looking at whatever’s happening right now, and not just social and cultural events, but everyday things. ‘Are you raising a kid? Are you taking care of your parents?’ We bring all that to the show … [Other artists] look inside for their material, and that’s fine, but part of what we do is look outside. We look for what we all have in common.”

To find out whether their audience has it in common, too, the band likes to test-drive material at the Birchmere, the Alexandria supper club that has served as the Babes’ unofficial home base for decades. (Smith’s husband, Michael Jaworek, is the club’s promoter.)

“It’s like a comfortable pair of shoes,” Smith says of the Birchmere, almost wistfully. A new song about orthopedics doesn’t seem far off.

Show: March 23 at 7:30 p.m. at the Birchmere, 3701 Mount Vernon Ave., Alexandria. $35.