The xx recently joined Tumblr in order to share their “inspirations + pictures + favourite songs” with an international and borderline-reverent fan base that has continued to grow in number since the band’s first release, “xx,” in 2009. The posts range from pictures of grey beaches and shattered glass to Four Tet remixes and Fleetwood Mac tracks.

It wouldn’t be surprising if the xx drew from just as wide an array of sources to create their sophomore release, “Coexist:” the album wavers uncertainly between the sparse aesthetic of their debut album and a more typical synth-driven pop record. The result is an occasionally confused but still enjoyable record from a band that seems unsure how to evolve without edging into the realm of mediocre ambient nightclub music.

On “xx,” the band wrote three types of songs: songs about being in love, songs about being in love at night, and songs about being in love and unhappy. “Angels,” the opening track on “Coexist,” falls into the first group, as Madley Croft croons, “And every day / I am learning about you / The things that no one else sees,” and ends on an almost-whisper. The song could have easily appeared on “xx:” a single sparkling guitar introduces Romy Madley Croft’s recognizably breathy vocals, while producer and band member Jamie xx’s thudding beat creeps in at the halfway mark.

“Angels” is the beginning of an album-long story arc that takes the listener through the ups and downs of a relationship. Madley Croft and Oliver Sim sing frankly and with authenticity about both intimacy and isolation: both “Angels” and the third track “Fiction” possess a warm wistfulness, as the singers describe the unhappiness that comes with separation. Halfway through the record, however, the lyrics grow more pessimistic as Sim drawls, “And now there’s no hope for you and me / My heart is beating in a different way.” As the album draws to a close, redemption is offered in the final track, “Our Song,” made both melancholy and hopeful by lines like, “You know I know you’re hurt / I want to mend your heart / And there’s no one else.”

The two singers navigate this storyline with varying degrees of success. On several songs, the emotions behind the lyrics are marred as Madley Croft’s previously clear, shimmering vocals morph into numb monotones or verge on whines. On “Reunion,” she sounds uncharacteristically off-key. Sim, in contrast, displays an expanded range and depth in his vocals as he and Madley Croft weave around each other, maintaining a compelling tension by overlapping and blurring their respective vocals together.

This unique dynamic is at times undone by jarring backbeats that are much more prevalent on “Coexist” than on “xx.” The band, drawing inspiration from club music, attempts to blend its signature use of silence and space with pronounced production from Jamie xx. However, the two styles do not always mesh well, as evidenced by the grating mix of pulsating club beats and steel drums on “Reunion.” When the combination does work, as in “Chained” and “Tides,” the sharp and distinct beat is highlighted by the silences that precede and follow it.

As “Coexist” draws to a close, listeners are lured back in as the xx step again into familiar territory. “Swept Away” features simple, striking guitar and piano chords as Madley Croft and Sim continue to converse in their rich vocals. And, on the closing track “Our Song,” the two singers are at their strongest, effortlessly harmonizing over an unassuming guitar and bringing the album full circle.

However, the band’s forays outside its comfort zone and into dance music are much less successful. The xx fared better when they sang about stars and night skies, and it’s hard to see those inside a smoky nightclub.

—Natalie Chang can be reached at nataliechang@college.harvard.edu.