One of the defining aspects of Bill Callahan’s post-Smog period is a willingness to experiment with lush arrangements. Both 2007’s Woke on a Waleheart and the new Sometimes I Wish We Were an Eagle feature prominent contributions from instruments that would have sounded way out of place on Callahan’s decidedly sparse early material. Eagle is littered with this kind of arrangement, especially in the opening six tracks. Callahan’s vintage slow-burn folk-rock intersects gorgeously with beautiful contributions from strings, brass and even some vaguely Middle Eastern woodwinds.

Experience seems to have taught Callahan better ways to fill the space between bellows of baritone, but his entrancing voice remains the definite centrepiece. A prime example is “Eid Ma Clack Shaw,” an elegiac lament of some unspecified lost love — my best guess is that it’s a recently departed horse named Boxer, but that could be way off.

Regardless, the outcome is a staggeringly beautiful account of the struggle to overcome emotional torment, and it includes Callahan’s vivid description of a dream in which he pens the perfect song: “I woke halfway and scribbled it down/ and in the morning what I wrote I read/ It was hard to read at first, but here’s what it said.” Then, he starts singing the nonsense-speak of the song title. Only a true master could turn gibberish (could it be horse-speak?) into one of the most memorable choruses in recent history.

Longtime fans will find a rare treat on the second half of the album, which includes material that sounds more like typical Smog than anything on Whaleheart, or even on the last few Smog albums. Churning, heady and repetitive, “All Thoughts are Prey to Some Beast” never deviates from its simple melodic structure. Instead, Callahan raises the hair on his listeners’ arms by drawing on a vast spectrum of vocal textures to tell his bold tale, throwing in the chirp of a violin or the twang of a brash guitar here and there for good measure.

With so many layers and so much going on in every song, it’s hard to single out only one or two highlights. Like all of Callahan’s recent work, its quality and consistency verge on being unsettling — if it weren’t so easy to lose oneself in his music, it would be disturbing to grasp how great a songwriter the man has become.