Lucinda Williams is road-testing some of her new material during live shows, including the stone-country duet "Jailhouse Tears." She's considering asking Hank Williams III or The White Stripes' Jack White to sing the track with her when she returns to finish it in the studio.

Lucinda Williams is finally learning to let go.

Known in the '90s as a perfectionist who nit-picked down to the nitty gritty, the singer-songwriter is now releasing strong records without spending years in the studio fretting over the most minor sonic details.

The change came after the critical and commercial reaction to her fourth album, "Car Wheels on a Gravel Road," a record she finished, scrapped, re-recorded, scrapped again, then released on her third attempt.

"Right after I recorded 'Car Wheels' I was really upset about my vocals," Williams says from a hotel suite in Burbank, Calif.

"I kept saying, 'I don't like my vocals.' Then I get a Grammy and the record goes gold, and I'm going, 'Wow. All these little things that I worried about, I guess nobody really notices them.' "

Williams brings her collection of gripping alt-country songs to the House of Blues at Mandalay Bay on Thursday.

It's an opportunity to experience a perennial critics' darling. (The New Yorker deemed her worthy of an 11,000-word profile.)

While Williams' slurred drawl of a voice is compelling, it's her songwriting skills that net her the adulation.

During a 30-year career, she has carved out an engaging and broad song catalog.

Williams has written break-up songs both acidic ("Changed the Locks") and winsome ("Metal Firecracker"). She has penned vivid accounts of friends' suicides ("Pineola" and "Sweet Old World") as well as country-pop tunes that became hits for Mary Chapin Carpenter ("Passionate Kisses") and Patty Loveless ("The Night's Too Long").

Her finest moments on record are borne of her rare ability to emote heartache and lust with equal abandon.

"Baby, sweet baby, kiss me hard/Make me wonder who's in charge," she sings on the slow-burning title track from 2001's "Essence," the album that prompted Time magazine to name her America's best songwriter.

Mainstream popularity has eluded Williams for most of her career, with radio programmers uncertain what format her unique blend of folk, country and rock fits into.

But with an expanding fan base, the 52-year-old has been selling out shows across the country, no small feat in a slumping concert industry.

"I'm kind of reaching the peak of my career just now. I don't know how that happened," Williams says, laughing. "I feel like I'm writing the best I've ever written."

Before her current tour kicked off, she laid down two dozen new tracks in March with plans to cull her album from the best material. She's been debuting some of the songs live.

"It's a real eclectic mix of stuff. I've got some real stone-country songs, kinda like George Jones, Loretta Lynn-style," she says. "I've got some real edgy rock songs, sort of like 'Essence,' like 'Changed the Locks,' and I've got some ballads."

Among the new songs is "Jailhouse Tears," an audience favorite even though it has yet to be released.

"I wrote it like a conversation, a duet, but I don't know who's going to sing it with me on the record," she says, adding that Hank Williams III and the White Stripes' Jack White are two names that have been floated as possible partners.

Another of her new songs is drawing comparisons to the work of the late jazz-soul diva Nina Simone.

"I'm really into old-style jazz," she says.

Excited about her new songs, Williams wants to work more of them into her sets. But she is careful not to do too much previewing.

"The fans have an emotional connection with the older material, and I have to appreciate that," she says. "When I go see Bob Dylan, I wanna hear all his old, cool stuff from the '60s, so I understand."

Until she can get back into the studio to finish her as-yet untitled new album, Williams is concentrating on her live show.

She blanches when asked about her June 2002 appearance at the Joint at the Hard Rock Hotel.

Only three songs into her set, a clearly nervous Williams told the audience, "I just can't do this. Y'all can have your money back." She then walked offstage.

Williams explains that her voice was a wreck that night, and says it's the only time she's ended a concert prematurely.

"It was one of those fluke things," she says, clearly still embarrassed about the episode.

"I really have to baby my voice."

She says despite that miss, she's still got a good track record.

"You should consider how long I've been playing, and that that's the only time I ever had to do it."