For a proggy sludge metal act, incorporating hooks into chunky riffs can be tricky. After the ambitious mixed bag of Yellow & Green, Baroness pulled off the transition on Purple. The album embraced catchy vocal melodies and sonic detours without forsaking bulldozing heaviness. Baroness’ evolution continues boldly on Gold & Grey, presenting a 60-minute, 17-track excursion into the band’s most left-field, yet most catchy territory. While its production value and stylistic ventures can come off jarring, Gold & Grey is a crucial foothold for Baroness in its pursuit of challenging, exhilarating expression.

Right from the start of “Front Toward Enemy,” it’s clear Baroness wants little to do with its past. Bassist Nick Jost takes a more pronounced role in the band’s sound, adding intuitive harmony and acrobatic licks to his growling tone. With this low end support, John Dyer Baizley and Gina Gleason reach beyond crunchy riffs. The results are more akin to prog rockers like Rush than anything sludge-related. The addictive drum and bass groove of “I’m Already Gone” allows the guitars to assume an almost ambient roll during the verses. The reverbed guitar chords send the chorus into the stratosphere, but it’s still played for taste rather than flash. These alterations serve a renewed fixation on sung melodies to a tremendous effect.

“Seasons” is where the new sonics can become disconcerting on first listen. Psychedelic ambiance builds over Sebastian Thomson’s propulsive break beat. The first real riff doesn’t enter until almost two minutes in. This building tension gives the shreddy instrumental break and the wall-of-sound in the half-time chorus a real sense of catharsis. Similarly, “Throw Me an Anchor” balances a Boston-esque chorus with dexterous math metal verses. Baizley and Gleason’s vocals work equally well in both contexts, becoming the glue for a bipolar arrangement. Robustly harmonized and dynamic, these two rise to the occasion on this bold departure from heavy duty riff-mongering.

Gold & Grey features six interludes that each center on a unique soundscape. Whether it’s the collage of keyboard and guitar arpeggios found on “Sevens,” the reverent choral vocals and flanger-tinged strings of “Anchor’s Lament” or the 41-second neo-psychedelia number “Crooked Mile,” these fleeting explorations are more than transitional tracks. The respective noisecore and spacey ambience on “Can Oscura” and “Assault on East Falls” provide yet more vital twists, a necessary ingredient on an album full of boundary-pushing.

The ethereal acoustic intro of “Tourniquet” recalls ‘70s prog ballads, even as the full band enters the mix. The chord progressions evolve alongside hooks and leads, leading to a deliciously old-school dual guitar solo. Even when “Broken Halo” steers closer to Baroness’ heavier roots flavor, the musicians still know to hold back for sticky hooks. Nowhere is this more apparent than on “Borderlines.” Bass and guitar spiral in agile hammered note riffing, but they’re more of a hyper-technical foundation for bluesy swing drumming, Sabbath-esque fuzz and soaring vocal melodies. Still, some of Gold & Grey’s gems come on its most intimate moments.

Without drums or distorted guitars, “I’d Do Anything” guides a slow-burn crescendo with bottom-heavy piano notes, layering drowning ambience over acoustic strums. “I’d do anything to feel alive again,” Baizley and Gleasen cry over the somber atmosphere, showing incredible vulnerability by heavy metal or prog standards. Folksy clean electric guitar lines of “Cold Blooded Angels” achieve a similar quality: “Now I miss the bitter hell/ That cut me down/ All the way to nothing.” As urgent percussion creeps into the somber acoustic vibe, the song jumps out from murky psychedelia into victorious guitar strains and dynamic drum fills.

The songwriting on display throughout proves the band doesn’t need overt intensity to get its point across. “Emmett-Radiating Light” takes on a rustic timbre with somber baritone singing, but gothic piano, chimes and nocturnal field recordings gradually replace the songs’ dense fingerpicked chord progression. “Pale Sun” even ends the album with an inexplicable combination of Pink Floyd and My Bloody Valentine. Vocals, guitar and bass commingle into a final blissful wash, proving Gold & Grey’s pivotal importance in Baroness’ evolution.

Those who miss Baroness’ savagery will find little of it here, but the loss of head-banging riffs reveals new and exciting facets of the band’s musicality. With an expanded sonic reserve, standard-setting arrangements and memorable motifs, Gold & Grey is a must for fans of powerful, nuanced, proficient rock.

Follow editor Max Heilman at Twitter.com/madmaxx1995 and Instagram.com/maxlikessound.