The sixth and final album from the boundary-pushing folk/Americana duo Brown Bird begins, fittingly enough, with dirgy, mournful strumming on a lightly electrified guitar that brings to mind what, say, Mark Lanegan feels like on a particularly downcast Sunday morning.

Like several songs on Axis Mundi, the reverb from the amp tailing lightly within the space of the room in which it was recorded gives the music an immediacy that's almost too close for comfort. Of course, this is the kind of "discomfort" that we look for in music, the kind that puts us up close and personal with the people who made it and makes it impossible to keep a casual distance from what they were going through when they made it.

As previously reported, Axis Mundi arrives after the death of Brown Bird's David Lamb, who played and performed with his wife, Morganeve Swain, until he passed away from leukemia last year. As such, the music takes on added gravity when the first thing Swain sings on the album is, "Tethered to the cure / I focus on the pain / If this flesh would fail / Devour me from within / May then my soul prevail / Free to roam again."

Needless to say, the spectre of mortality hangs over Axis Mundi -- which was named after the phrase for where heaven and earth meet.

Other than "Tortured Boy," which Swain wrote about the first stages of her relationship with Lamb, all of Axis Mundi was written during the time leading up to Lamb's diagnosis, as well as when he underwent treatment. Nevertheless, certain moments, such as the odd-timed gypsy-footed shuffle of "Bannermen," come across as downright celebratory. Axis Mundi, in fact, showcases how much Swain and Lamb had come to push their sound into Middle Eastern, Eastern European and even heavy metal directions while writing this material. As such, the album comes across less as a closing chapter than the sound of a band hungry for new modes of expression.

It's hard to imagine anything worse than a creative or life partner passing away. But with Axis Mundi, Swain and Lamb make a bold, assertive -- and lasting -- statement about change, and about the temporal nature of life and  attachment. For their final statement, Brown Bird manage to navigate trepidation, weariness, resignation, determination and curiosity with the kind of musical agility that supports their mixed emotions and makes them all the more textured, vivid and real.