“Joyful and triumphant!” Those words from “O Come All Ye Faithful” nicely describe Mac Powell’s uplifting vocal performances on Third Day’s Christmas Offerings. His burly, vibrato-tinged singing is at the center of this mix of traditional carols and original tunes. The band’s neo-Southern rock sound is an appropriate fit for the classic material, bringing out the Old World melodic grace of “What Child Is This?” “Angels We Have Heard on High,” and “The First Noel.” Powell taps into his best backwoods preacher voice for a passionate “Silent Night.” The newly composed material is strong, with “Jesus, Light of the World” (a rough-hewn invocation of the Nativity) and “Born In Bethlehem” (an inviting, acoustic-driven number) particular standouts. Third Day strikes a modern note in “Christmas Like a Child” (a plea for renewed innocence in a fallen world) and “Merry Christmas” (a sensitive portrait of a Chinese orphan girl). Rock bands — even Christian ones — are often on shaky ground when they attempt a Christmas album, but Third Day’s Christmas Offerings is both deeply reverent and artistically impressive.