Dar Williams has always been into theater — which means regularly trying to play somebody else. It wasn’t until a few years into her career as a singer-songwriter, when she was performing at Christopher’s in Porter Square, that she grabbed hold of what would prove to be her most successful role. The day of the Christopher’s gig, she recounts, " I was actually just really angry at somebody. I wasn’t able to spend that whole day thinking of who I would be on stage. I just remember just sort of ad-libbing. "

It was a major breakthrough night for Williams. She discovered talents and abilities — from disarming stage patter filled with sincerity and humor to a willingness to take chances — that have served her every bit as well as her rich, radiant, slightly breathy vocals. She’s maintained a rabid following and six-figure record sales, a rare accomplishment for a folksinger signed to an independent label. Her latest CD, The Beauty of the Rain (Razor & Tie), is her sixth, and she’s made memorable guest appearances on CD tributes to Bruce Springsteen and Nick Lowe. The disc hovers between folk and pop, with guest artists including jazz keyboardist John Medeski, bluegrass star Alison Krauss, banjo shredder Béla Fleck, Blues Traveler’s John Popper, and bassist Stefan Lessard of the Dave Matthews Band.

Although those talents cover a lot of territory, Williams is something of a bridge between the old folk and the new. She’s done benefits for Native Americans, solar power, and the pro-hemp people. When giving a private performance for Supreme Court Justice Sandra Day O’Connor last year, she made a point of thanking O’Connor for helping to protect reproductive rights. These days, Williams is working on a complicated effort to eliminate reliance on the Indian Point Nuclear Power Plant in Buchanan, New York. ( " Joni Mitchell paints, " she jokes. " I like to come up with multi-tiered programs. " ) But she’s also more contemporary, more personal, than the old-fashioned folkies.

Williams spent two and a half years scuffling around the Boston folk scene in the early 1990s, paying two bucks to play two songs at places like Catch a Rising Star in Cambridge and the Naked City Coffeehouse in Allston. " I was part of a scene for sure, " she recalls. " It was competitive, sometimes a little bit silly. " She reels off the advice she got on the coffeehouse circuit. " Somebody told me I should quit. Somebody told me I shouldn’t sing falsetto, because my diction was bad. Somebody told me I had to get guitar lessons. Somebody told me not to drink so much water on stage. "

She moved to Northampton after leaving her job as a stage manager for Sarah Caldwell’s Opera Company of Boston; now she lives in New York City, where The Beauty of the Rain was recorded. She says the new disc is more or less about the transition from New England to New York. It benefits from her deepening connection to producers Stewart Lerman and Rob Hyman, who worked with her on her previous album, 2000’s The Green World (Razor & Tie). They grabbed Fleck, Krauss, Popper, Medeski, and fellow folksinger Cliff Eberhardt as they came through New York on their own rounds. " All are recognized as experts at what they do, " Williams points out, " They all have good reputations as collaborators — and as kind people. " Of Popper, she says, " I heard him before I met him. He arrived at the studio early — which never happens. " She had not yet come through the door when she heard his distinctive rasp working out on " I Saw a Bird Fly Away, " a swift-moving number with idiosyncratic lyrics like " The tabloid tainted actress knows the myth of higher ground. " As she recalls, " I was standing outside the studio hearing him sing my song, and he made it sound like he’d written it. "

The new album’s title track is an introspective number that falls on the folkier side of the folk/pop divide, Williams matching the rhythm of the words to the accents from smooth jazzman Chris Botti’s muted trumpet. Elsewhere, she relies more on instinct. " Whispering Pines " — a Williams original, not the old country chestnut recorded by dozens of folks over the years, but a number by the Band — was, she remembers, " one of the quicker ones " to record; she adds that she was " almost in a trance " when she laid it down. Sometimes, she says, " you are thinking about your laundry " when you perform. " Sometimes you are listening with a deeper ear. That song renewed my faith in engaging the best you can, without thinking so much. "

Dar Williams plays the Orpheum Theatre this Saturday, April 12. Call (617) 931-2000.