Have you ever been afraid to listen to a follow-up album? It can be like seeing someone you used to be wholly, wackadoodle-in-love with after a long time apart. The rationale: He or she must have changed. You steel yourself for the disappointment, as well as awkwardness, lack of enthusiasm and chemistry. But at the same time, you hope there's still something there. You ask that some residual giddiness or fervor exist, so that the narrative of love in your life will make some sense, your old vulnerability (maybe) justified. Anything less could threaten what you've done and how you've felt in the past.

Many fell in love with For Emma, Forever Ago, Bon Iver's first album, when it came out in 2008. Aside from the music, the myth itself was unbeatable: A lone, rugged, sad man (Justin Vernon) heads off to a cabin in the icy Wisconsin woods after the dissolution of his first band, DeYarmond Edison, and hibernates for three months, strumming and singing his way through heartbreak. He brings one small, dynamic microphone and one steel-string acoustic guitar, working in isolation, building layers and layers of swelling, high-pitched harmonic howls over sparse, percussive chords. Through this, he finds a way of creating music that makes his constraint, his pain, palpable in the space between the two.

Since then, Bon Iver has, indeed, changed. A collaboration with Kanye West later, news of Vernon's affinity for auto-tune perhaps troubled some, or made others fearful to listen to an artist that had crafted so much out of self-imposed limits and a respect for simplicity. But if the new album is more expansive than the first, it's also more exhilarating. Its beauty has less to do with a monastic sort of grief, a restraint and sparseness where the emotional hollows can be felt—and instead it has everything to do with opening up the process to collaborators, letting the music find new, exquisite, meandering and subtle ways of expressing itself.

Immediately, Bon Iver is slicker and more flush with production and instrumental complexity than anything on To Emma. Vernon hired bass saxophonist Colin Stetson and pedal-steel guitarist Greg Leisz to collaborate, and he introduced a fair amount of synths, electricity and some surprising but welcome new rhythms. It's true that this newfound freedom has made for work that's as challenging as it is triumphant. Some sounds (perhaps the guitar tone, perhaps the sexy sax) especially on the first and last tracks, "Perth" and "Beth/Rest," flirt dangerously with cheesiness. On the other hand, the music doesn't linger here, quickly transitioning to plucky, muted riffs, some reggae-like downtime in "Minnesota," and right back to bright acoustic fingerpicking.

But where "Perth" and "Minnesota" can be unexpected or uncomfortable, the album's next three tracks, "Holocene," "Towers" and "Michicant," relax into superb syntheses of Bon Iver's new library of sounds, the sax and synths present, but only enough to be supportive of emotive guitar work and controlled delicacy of Vernon's vocals. The poppy, pretty electric guitars on "Towers" are perhaps most recognizable as old-school Bon Iver; the lilting, electric waltz of "Michicant" continues this way, and it marks itself as perhaps the most poignant, dynamic track of them all.

Some things haven't changed. Bon Iver was recorded at an abandoned veterinarian's office, the studio constructed over a waterless pool, so the penchant for quirky, mythological isolation is there. But Vernon has staked himself out as an artist from whom to expect constant innovation, continuous wonder and curiosity toward the new—so much so that, in the end, with another emotional roller coaster of an album under his belt, distinctions in his technical approach seem like just that: minor technicalities.