BEFORE: one look at Jane Monheit and you know that jazz vocals aren't just about the music.

Jane Monheit and Madeleine Peyroux have a better stake than most jazz musicians in crossover success. Vocal albums always get the edge over instrumental, whether the style is jazz or not. Give us words to go with the fancy tunes and improvisations. And it doesn’t hurt if, as venerable jazz producer Orin Keepnews once said to me about Diana Krall, she "works her tail off" but also happens to be "a pretty blonde lady." With the right ingredients, the typical jazz "hit" of 30,000 copies (a "miss" that would get any rock band fired from their major-label deal) can cross over into sales of the hundreds of thousands.

The means to that commercial end are many. Cassandra Wilson broke the ceiling on serious jazz sales with Blue Light til Dawn (Blue Note, 1993) by cracking the 100,000 mark. There followed Krall and then, of course, the Great Norah. Wilson broke all the rules of jazz vocal albums, creating something as progressive as it was accessible: no piano, no saxophones, but plenty of acoustic guitar and wide-ranging repertoire. And Jones, working with songwriter Jesse Harris, came up with a kind of latter-day Charlie Rich jazz treatment of country-fied originals.

Monheit hasn’t broken into the commercial stratosphere, but she has a broad-based audience for her repertoire of Broadway standards presented by traditional jazz combos in traditional bop-era arrangements. Yes, she works her tail off, and, to paraphrase Keepnews, it doesn’t hurt that she’s a pretty dark-haired lady with full, luscious lips, eyes that are deep-dark pools, and a voluptuous body that . . . oh, never mind, you get the idea. In 1998, Monheit, was first runner-up, at age 20, of the prestigious Thelonious Monk Institute vocal competition. There followed three releases with the independent N-Coded Music; now, at 26, she’s making her Sony Classical debut with Taking a Chance on Love, and next Friday, she’ll be making her third visit to Sanders Theatre.

Peyroux released Dreamland (Atlantic, 1996) at age 23. She sang her share of covers on that album — everything from the Patsy Cline hit "Walkin’ After Midnight" and "I’m Gonna Sit Right Down and Write Myself a Letter" to "La vie en rose" — but also a small handful of solid originals. Most striking at the time, though, was her resemblance, not just in rhythm and phrasing but in timbre, to Billie Holiday. Her album hit, selling 200,000 copies. She toured briefly, then disappeared. Now she’s back with the new Careless Love on Rounder.

When I talked to Monheit and Peyroux recently, it was interesting to compare their backgrounds and approaches. Monheit is a sort of girl next door from Oakdale, Long Island, whose æsthetic is driven by her love of American musical theater — in a different generation, she might have been a Broadway star. It’s easier to see Peyroux, on the other hand, fitting in with the misfits of American indie rock. Whereas Monheit lies back on the cover of Taking a Chance on Love, one arm behind her head, those full lips slightly parted, giving the camera a come-hither look, Peyroux on the cover of Careless Love is photographed in a full portrait sitting on a chair in an alley, wearing a party dress whose skirt spills to the ground but is gathered around her calves to reveal bare feet; she looks almost glum. A ceramic pot of red flowers is by her side, one of them pulled from the bunch and lying on the pavement. If Monheit is sweet foreplay, Peyroux is the morning after. Jazz, we say, is "all about the music," but vocal performances are always about more.

Whatever you say about Diana Krall, she sees herself as a jazz musician first, a pianist and student of Jimmy Rowles. Monheit is first and foremost a singer, one whose material just tends to go in the jazz direction, a girl with a retro-affection for the musicals she grew up watching on video, like The Band Wagon and Kiss Me Kate, both of which she draws from on her new album. Her effusive brief liner note to Taking a Chance on Love says that the material is in part a tribute to the MGM movie musicals. On the phone from a tour stop in Milan, she tells me that The Band Wagon, the source of the CD’s Howard Dietz/Arthur Schwartz composition "Dancing in the Dark," "is my all-time favorite, like, the holiest of holies." Starring Fred Astaire and Cyd Charisse, the Vincente Minnelli film came out in 1953. That was the year, likewise, of the MGM film version of Kiss Me Kate, the Cole Porter musical from which she gets "Why Can’t You Behave." How did she get exposed to such old music as a child? "Mostly my mother would rent them for me."

Monheit says she sang in "millions of rock bands" in high school and college, and she’s expressed a taste for Nine Inch Nails ("I used to be totally goth in high school for about five minutes"), and these days says she’s "a little obsessed" with Björk’s Vespertine. "Her way of expressing herself is completely unique and original." And yet, "I always knew I wanted to be a jazz singer. It’s sort of what’s closest to my heart. If it were a perfect world, I could just mix genres all day long and never categorize myself, but, you know, because of the way things are, you have to focus on just one thing. So obviously, jazz was the answer for me, without even thinking about it."