“There are only two kinds of songs,” Townes Van Zandt said, well before he died. “There's the blues, and there's zip-a-dee-doo-dah.” The new Son Volt album is titled Notes of Blue. Simple as that, maybe. Just now pushing fifty, Jay Farrar, the creative force behind Son Volt, is still not as old as his voice. Not nearly. His singing voice, an ageless gift which sounds something like old timber looks, like the unpainted walls framing Walker Evans' best portraits from Let Us Now Praise Famous Men: simple, durable, weathered and grooved and unplanned.