“You can’t play a sad song on the banjo,” Steve Martin once keenly observed, and his maxim holds true in the music of Riverwest’s perky seven-piece The Candliers. They write bittersweet odes to times long past, then cheerfully play the hell out of them, nodding to old-time ragtime and swing music. They’ll do a 7:15 p.m. show at the Cascio Groove Garage.