You wouldn't expect Tucson to be the home of an important new Celtic folk band, but that's just what the Mollys are. From the Southwestern desert comes the quintet's new album, "Hat Trick," which is full of spirited pub songs, pushed along by accordion and mandolin licks straight out of the emerald hills of Ireland. If singer-guitarist Nancy McCallion supplies the Irish American influence in the band, her partner, singer-mandolinist Catherine Zavala, supplies the Mexican American influence, and the two traditions get along famously, sharing an enthusiasm for squeeze-box polkas and barroom ballads.

To describe the Mollys as an ethnic folk band, however, is to put them in a box too small for their talent. McCallion has evolved into a major-league songwriter, deserving of comparisons to Gillian Welch and Iris DeMent. McCallion takes much more of a wisecracking, bawdy approach to the world than her two peers, but her songs are no less substantial for it. In much the same way that Welch and DeMent have used hillbilly music as a vehicle for their personal stories, so has McCallion used the forms of Celtic and Tejano music for her distinctive take on love and work.

She has quite a way with lyrics, comparing a lover's promises to the exhaust of a departing bus and describing a seducer as "half sincere and half undressed." More crucially, she evokes the dilemma of young women who yearn for love and sex but distrust the small towns and shortsighted men where they must find them. Even more than her words, McCallion's music conjures up those inexorable desires in driving rhythms and sing-along melodies. When she cries, "I don't wanna go to bed, ain't nothin' happened yet," her ringing soprano implies she's about to make it happen on her own. Appearing Friday at Catonsville Community College and Thursday at Twist & Shout. To hear a free Sound Bite from the Mollys, call Post-Haste at 202/334-9000 and press 8127. (Prince William residents, call 690-4110.)