Like skinhead punk or bluegrass, zydeco — the jubilant R&B branch of Cajun music — is an intrinsically narrow art form; there’s only so much you can do with it. That hasn’t stopped major labels from scooping up some of zydeco’s leading lights now that it’s in vogue. On Louisiana Music, accordionist-bandleader Rockin’ Dopsie (a.k.a. Alton Rubin Sr.) offers a virtual primer on roadhouse zydeco, from the cover of a song by founding father Clifton Chenier to the tugboat-like squeeze-box, scraping washboard, and hard-as-floorboard grooves. The album doesn’t offer any surprises. B-