You could mistake JD McPherson for a revivalist, given how few other contemporary artists are likely to assert, as he boldly does, that “’Keep a Knockin’ by Little Richard is the best record ever made. But in a very real sense, McPherson is much more a pioneer than roots resuscitator. He’s knocking at the door of something that arguably hasn’t yet been accomplished—a spirited, almost spiritual hybrid that brings the forgotten lessons from the earliest days of rock & roll into a future that has room for the modernities of studio technique and 21st century singer/songwriter idiosyncrasies. Let the Good Times Roll, his second album, is a stranger, and more personal affair than its Fats Domino-redolent title might at first suggest.