A Night Out With Friends : Pals Shawn Colvin and Mary Chapin Carpenter share a stage--and good times.

What’s the best part about being the opening act for a close friend’s concert? “You don’t have to be tense about wanting to make sure the other act thinks you’re good,” says singer-songwriter Shawn Colvin, who will precede her longtime pal Mary Chapin Carpenter on stage Sunday at the Greek Theatre.

Colvin, who has sung on many of Carpenter’s albums, clearly passed that audition a long time ago. The two have the same manager, who suggested they share the bill during Carpenter’s current tour supporting “Party Doll and Other Favorites,” her recently released collection of hits and rarities.

“We don’t get to see each other that much, so it’s good to hang out,” Carpenter says in a separate interview. “But also, I just love Shawn’s music.”

This mutual admiration could make for perfect harmony all summer, but Sunday is the last of only three “Party Doll” dates for the pair, after which Colvin departs for her solo acoustic tour and briefly joins the Lilith Fair in July.

Though each artist has her own style, both play well-crafted, thoughtful, roots-influenced pop, ranging from folky ballads to upbeat rock, that appeals to a range of mainstream listeners. Both have a winsome, casual stage presence, with Carpenter’s shows often incorporating audience sing-alongs and surprising choices of songs.

“We always sit in with each other,” says Colvin. “Since we’ve known each other so long, we know a lot of [each other’s] stuff.”

Both performers plan to release new albums in 2000, so concertgoers can expect to hear fresh tunes. Carpenter, who hopes to enter the studio early next year to record her first collection of new material since 1996’s “A Place in the World,” road-tests her songs whenever possible. “It definitely works the kinks out,” she notes with a laugh.

Assembling the “Party Doll” compilation also made Carpenter consider how many songs “really do lend themselves to new interpretations and deconstruction,” she says. “With ‘Quittin’ Time,’ the original version’s a much more jangly, up-tempo thing,” while the “Party Doll” variation is the subdued rendition recorded during an acoustic tour.

Carpenter took a similar approach to the album’s title track. The song, from Mick Jagger’s solo album “Primitive Cool,” is a concert favorite she’d always wanted to record. The original live performance was “almost like a send-up, a more rock ‘n’ roll version,” she says. “But in the studio, it just didn’t happen without an audience.”

She experimented with “stripping it all down, and slowing it way down,” and crafted a different version to record. Now, she says, “the version we’ve been doing live starts out very quiet, much like the record, and then morphs into the way we used to do it in concert.”

Colvin says she works on her own forthcoming album “whenever there’s a free moment.” She has again teamed with producer and songwriter-guitarist John Leventhal, along with musicians from “A Few Small Repairs,” her million-selling 1996 Grammy winner.

“All my records have had a lot in common. But we like to push the boundaries a little bit, each time,” she says, adding wryly: “We’re working on a song that has something in common with the Backstreet Boys, so there you go.”

But before recording is completed, Colvin will join Bonnie Raitt, Jackson Browne, Bruce Hornsby and David Lindley for a collective tour in September. They’ll take turns singing songs in a group format. Colvin sees it as “an opportunity to have fun with each other’s songs,” fondly recalling a similar venture with Richard Thompson in 1991. “I did my opening set, and then I’d play rhythm guitar and sing harmony in his band,” she says.

Although she enjoys the spotlight, says Colvin, “It’s great to take a step back. I just love being a harmony singer,” a pleasure she expects to indulge on Sunday. “Musically, it’s fun to be a contributor, and not the frontperson, but it’s also just kinda cool. You don’t have to sing every minute. You can work on your moves.”

BE THERE

Mary Chapin Carpenter and Shawn Colvin, with Solas, Sunday at the Greek Theatre, 2700 Vermont Canyon Road, 7:30 p.m. $17-$35. (213) 480-3232.