The hazy-nostalgic sound of many recent indie-pop bands has hardly ever been more explicitly acknowledged than in the title of M83’s new two-disc album, “Hurry Up, We’re Dreaming.” The album is a mature addition to M83’s storied discography. In an interview in Spin Magazine, lead singer Anthony Gonzalez said the album is “mainly about dreams, how every one is different, how you dream differently when you’re a kid, a teenager, or an adult.” Artistically, the album is an articulate expression of dream in sound. At times, however, the album’s excessive length serves only to accommodate long and indulgent ambient sections that disrupt the otherwise coherent sequencing.

”Hurry Up, We’re Dreaming” is structured around a chronological approach to a person’s dreams over the course of his or her life. The album starts by describing children’s dreams through fanciful sound. One of the highlights of this collection is “Raconte-Moi Une Histiore.” The sharp claps guide the light-hearted synth into deeper basslines and then seraphic ambiance while a child’s thin voice delivers an endearing monologue about a magical forest frog. Yet the album’s introductory section is not particularly consistent. The very next track, “Train to Pluton,” is completely electronic and slows the pace of the album. This is the sort of song that would have been deemed unnecessary for inclusion on a one-disc album, and it serves little purpose conceptually or musically.

The album builds in momentum over its evocation of adolescent dreams. “OK Pal” is the most distinctive song of the sequence. The track is catchy, and reminiscent of Phil Collins’s production. It’s steeped in the exuberance of a storybook, adolescent relationship, and features a female monologue about the nervous anticipation leading up to her first kiss. “Splendor,” another gem of the album, conveys both the excitement of going away from home and the ominous feeling of striking out into the unknown. “Another Wave From You” is an example of the better purely electronic tracks. Its surrealism is well positioned, as it builds engaging tension during the midsection of the album. But “Year One, One UFO,” another electronic track, seems out of place. Its fast pace, heavy drums, and folk transitions give the sense that M83 is artificially diversifying the sound of an album that is beginning to sound lengthy and unfocused.

When properly focused, though, it is this very eclecticism that makes the album. The later sections are a full transformation of tone which exhibit M83’s incredibly flexible style. “Steve McQueen” is a beautiful track, and even features brief hip-hop arpeggios. Where other tracks were hopeful, forward-looking, and wistful, “McQueen” speaks to perseverance and strength. It is the practical dream of a father who longs to provide for his family. “Klaus I Love You,” the penultimate song of the album, is a peek at dreams to come. The track is one of the album’s best, but its location on the album is indicative of some of the larger issues with “Dreaming.” Through the last songs, M83 affects jarring transitions from the more serious numbers back to their earlier, light-hearted pop sound, and these missteps replicate in miniature the album’s issues of overwhelming, indulgent breadth.

“Hurry Up, We’re Dreaming” is a strong album with excessive frills. While at times it feels like it loses focus or could have been cut down, it offers a compelling account of dream in sound. In the midst of an ambitious artistic vision M83 stays true to pop music with a number of simple earworms. Though the album’s ambitious aims are well-intended, its length and catch-all approach to genre are ultimately more hindrances to the better parts of the record than they are high-concept artistic choices.