Twenty years ago she was a fledgling lounge singer, dispatching vintage tunes amid the din of conversation at the long-shuttered Gold Star Sardine Bar, on North Lake Shore Drive.

Today, she stands among the most respected singer-pianists in jazz, a blossoming composer set to release the boldest and most substantial work of her career.

When Patricia Barber's "Mythologies" (Blue Note Records) appears in stores on Tuesday, listeners will hear a piece of music with no apparent model in jazz of the 20th Century (or the 21st). For though classically tinged jazz suites date back to at least Duke Ellington's "Black, Brown and Beige" (1943) and extend to epic works such as Charles Mingus' posthumously premiered "Epitaph" (1989) and Wynton Marsalis' Pulitzer Prize-winning "Blood on the Fields" (1997), "Mythologies" stands apart from such behemoths.

Diversity and coherency

For starters, it's an intimate, Schubertian song-cycle based on Greek mythology, as re-examined by an ancient Roman poet (of all things). Moreover, it pushes at the outskirts of widely accepted definitions of jazz, in that it encompasses a pop sensibility at one moment, classical expression the next and passages of hip-hop verse and triumphal choral writing, to boot.

Yet these far-flung expressions cohere surprisingly well in this suite -- just as they did when Barber performed the world premiere of excerpts of the work at the Museum of Contemporary Art in January. The alluring liquidity of Barber's vocals and the chic understatement of her pianism give the music its continuity, while the high craft of her lyrics bring it focus and purpose.

But the artistic heights to which Barber aspires in "Mythologies" may make this release more endearing to serious listeners than to the vast commercial audience, which has made icons of far lesser talents, such as Norah Jones, Diana Krall and Jane Monheit. While these artists have triumphed commercially by reviving role models of the distant past -- particularly the seductive, purring chanteuse of the 1940s and '50s -- Barber has ventured into fresher territory. To her, the female singer-pianist is not necessarily an object of nostalgia and romance but a contemporary thinker with intellectual firepower to burn.

Inspired by another innovative Chicagoan, the theater director Mary Zimmerman, Barber chose as inspiration Ovid's "Metamorphoses," which was the fulcrum of Zimmerman's celebrated stage play of the same name for Lookingglass Theatre, in 1998. Because a jazz composer-pianist does not have actors, dialogue and scenic design at her disposal, Barber has come to grips with Ovid's vast retelling of Greek mythology by crafting her songs as character sketches of particular gods or goddesses.

This conceit has enabled her to bring a jazz sensibility to a remote field of literature, yet she also has managed to transcend the source material.

In "Icarus," for instance, Barber predictably captures the heroic sweep of the young man's famous flight with surging rhythms and soaring melody lines. Yet she traverses beyond the celebrated narrative, as well, singing a verse that alludes to Nina Simone's earliest days as a struggling jazz singer. In so doing, Barber reminds us that great artists, too, take perilous risks in order to fly. Like all of Barber's writing in this suite, the Simone references prove subtle and hauntingly poetic.

In "Narcissus," Barber avoids the obvious theme of self-adoration and dares to explore, instead, the mirror-image qualities of homosexual love. And in "Pygmalion," she turns the heady yearning of an artist smitten with a cold-stone creation into an exploration of unrequited love.

Insomnia to gluttony

Musically, "Mythologies" covers a vast expressive range, from the brooding, late-night blues of "Morpheus" (in which an insomniac protagonist yearns for sleep) to the wicked, snarling satire of "Hunger" (an ode to gluttony); from the dirgelike gloom of "Orpheus" (who grieves the loss of Eurydice) to the glorious, redemptive choral passages of the finale, "The Hours."

Made possible by a Guggenheim Fellowship, which afforded Barber the time to research and create the magnum opus, "Mythologies" bears few similarities to her earlier work -- except that it represents the further development of her gifts as songwriter, which came to the fore in the aptly named CD "Verse" (of 2002).

Given the nature of any jazz musician's career, which requires a great deal of performance in order to stay solvent, it may be a long time before Barber again can find the time and means to devote to a work of comparable import.

Which makes "Mythologies" all the more valuable.