"This might sound spacey," says Andrew Harkin, bassist for New York-based Celt-rockers the Prodigals, "but sometimes music plays the musician." In this case, at least, it makes perfect sense. The Prodigals' sound -- a smooth but potent cocktail of rock and traditional Irish that's far more polished than the adopted descriptor "jig-punk" would suggest -- has remained consistent through three changes at the guitarist-vocalist slot in as many years. (County Cork native Eamon O'Tuama recently replaced Colm O'Brien, who left after the completion of the band's fourth album, this year's Needs Must When the Devil Drives. O'Brien had replaced Ray Kelly, who struck out on his own after appearing on albums two and three.) It helps that Harkin is the finest bass player in Celt-rock and that Greg Grene is as ferocious on the accordion as They Might Be Giants' John Linnell. Still, Harkin might be right -- something else might be at work. It's not like the oft-vacated position is unimportant in this band: Prodigals guitarists have always shared lead-singer duties with Grene. The personnel changes have been like "successive waves depositing sand on a beach," says Grene. "Each [new member] has built on what was there before." And accordingly, he promises that O'Tuama will not let down fans who've grown accustomed to the unusual rotation system -- Grene's cheerful lilt on some songs, O'Brien's and Kelly's rough-edged growl on others.