Mark Olson and Gary Louris' new disc may not be the Jayhawks reunion some fans hoped for, but it's a respectable set of mostly acoustic folk songs sweetened by the duo's bright, sibling-like harmonies. Most of the music here is slow and muted: In "Saturday Morning on Sunday Street," the two channel Simon and Garfunkel like they used to channel the Burrito Brothers. This isn't trailblazing work,...