NNENNA FREELON A word to the wise regarding six-time Grammy nominee Nnenna Freelon: She's just released a Christmas album, and this is a Christmas show. Whether this is a good or bad thing depends on how you feel about seasonal songs, unfancy jazz vocals and backing instrumentation that ranges from bongos to big band. But if you do like these things, then Freelon is the woman for you. An alto, she sings with impressive clarity, control and pleasure. And don't take the aforementioned unfanciness to mean that Freelon is unhip, or her phrasing unoriginal - quite the contrary. An artist who didn't even start her career until her late 30s, Freelon simply approaches her songs with a maturity that has always prevented her from over-selling herself. Her versions of yuletide classics sound fresh and joyful, lit from within and given a new sense of motion by her backing off, the brass especially. For jazz fans, this is a must-see. And for those unfamiliar with the genre, Freelon offers an ideal starting point. With John Brown Big Band. $29.50-$39.50. Dec. 15, 8 p.m. McGlohon Theater, 345 N. College St. 704-372-1000. www.blumenthalarts.org.