Short of smashing their instruments onstage, Willie Nelson and Wynton Marsalis probably couldn’t shock an audience at this point. But this 2007 live set offers numerous subtle surprises as the artists nudge each other out of their comfort zones. Prodded by Marsalis’ swinging quintet, Nelson discovers inventive ways of phrasing lyrics he’s sung a zillion times before, including a sly “Stardust,” and he uncorks darting guitar solos that underscore his debt to Django Reinhardt. Though trumpet-master Marsalis can sometimes be too dignified for his own good, he’s delightfully playful here. Just check out the scorching fills on “Night Life.”