“I want to start a fire / in your heart tonight / Oh tell me why do I so yearn to cause trouble,” Mirah sang over a saucy gypsy beat on her 2001 sophomore album “Advisory Committee.” On the her latest effort, “(a)spera,” there’s little trouble to be found.

Mirah warbles and moans as sweetly as ever, but some of the spunk seems to have been lost in the four years since her last solo effort. She’s made the metamorphosis from her more raucous indie-folk inspired early albums to a more mature singer-songwriter niche, but it’s not clear that the softer spirit allows her to express her full potential. The occasional ominous rumbling of drums or the wound-up melodrama of vibrating string sections hint at powerful release, but Mirah tends to fall back onto lovely but less memorable softness.

Mirah’s restraint seems set on driving home the pessimism underlying so many of her songs, as when she sings on “The World Is Falling”: “From here we crouch and watch the plunder of the world we built with sweat and love / Why were you not built for wonder? / Why will we never get enough?” Like 2004’s spirited “Jerusalem,” this track addresses the heavy subject of Middle Eastern politics. But unlike that uplifting peace anthem, this seems a forlorn meditation, full of loss rather than hope.

Melancholy pervades the album’s love songs as well. Sexiness and whimsy have faded in favor of mournful strains and cooing. On “Education” Mirah sounds more jaded, and a little less fun than in the past. On “The River” she sings, “tears so thick like glue they drip and build castles slow,” a statement that describes much of the album: slow songs that drip and blend into one another.

However, the castle she builds is a lovely one, and “(a)spera” is far from a disappointment. Mirah’s songs are lyrical blends of exquisite vocals for which the always varied musical accompaniment is like perfectly chosen punctuation. They coalesce to make a calm and collected sweetness.

And despite the overall softness, Mirah still infuses her mellow songstress sound with the more experimental. “Country Of the Future” is a trippy invitation to dance set to a carnival beat, and “The Forest” has a drum and horn-filled ending that lends it a satisfying hard edge. The globally-minded elements put her in the company of fellow folk-rocker Zach Condon of Beirut: tasteful sampling from a wide range of musical influences without ever seeming like world-music kitsch.

“(a)spera” ends with “While We Have the Sun,” featuring a tingling melody on a kalimba, underlining Mirah’s capacity to make pure prettiness from exotic and unexpected elements.

She ends the album on a hopeful note singing, “Sorry about all the sorrows.” It’s a tempered end to an album about the melding of beauty and pain, a conflict that ultimately comes down on the side of the pretty.

But the opening song might provide the best summary of the album. “Generosity” strikes closest to Mirah’s signature meld of melancholy and heightened sense of drama, but also teases us with what seems to be missing from the rest of the album. The song is about being drained and used up by love: “It was all of my energy / More than I wanted to give / I am empty.” She certainly bares herself in her lyrics, but not, it seems, in the music.

While out of her emptiness she makes some lovely sounds, the lack of energy is palpable through the album. As she sings in the refrain “I won’t give more,” the chorus responds with a justifiable desire: “We just want more.” “(a)spera” just doesn’t quite give enough.

—Staff writer Cora K. Currier can be reached at ccurrier@fas.harvard.edu.