Isobel Campbell gave up her role as “Belle” in Belle and Sebastian almost ten years ago, going a wholly different route as a solo artist and a collaborator with Mark “Screaming Trees” Lanegan. Their latest album of duets, Hawk, includes two numbers by Townes Van Zandt and contribution from Willy Mason. As with the duo’s other release, “Hawk” is uneven but largely a success. There are many powerful, moving songs like “Come Undone”, but there a few missteps that are so slow that they become dull (“We Die and See Beauty Reign”). These two are at their best when they have a lot of give and take, and when the tempos change, because both of them have fairly even delivery. Nobody’s belting out a scream or a big Aretha wail here. Creepy, atmospheric blues is the best use of their talents. Like Lanegan’s extreme, vibrating bass against Campbell’s hopeful, airy quality on “Time of the Season” (not a Zombies remake). And when they hit their marks, like on “No Place to Fall” and “Get Behind Me,” it’s as touching as a Tom Waits role in a Jim Jarmusch film. It’s worth having on your shelf, for sure.