On X&Y, Coldplay reach for the stars. Not since the heyday of prog has a band gone so Carl Sagan on us. More than one song mentions either planets, outer space, or being ”part of a system I am, I am,” as Chris Martin croons in his buttery falsetto. The references are fitting, since Coldplay have never sounded so celestial. The music swells with grand gestures (sky-piercing guitar solos, multiple keyboards, and let’s-try-this-approach fussiness); Martin’s voice is often multitracked into a one-man choir. The band seems to have fully digested the rock-star manual that demands third albums be major statements of artistic growth. Coldplay are an arena band now, and on X&Y, they truly come across as one.

The lofty goals suit them, but only part of the time. As much as Norah Jones, Coldplay come from the music-as-balm school. So Martin’s latest batch of lyrics dwells on repairing communication breakdowns and pep talks for those in need of solace or confidence building (”You don’t have to be on your own/You don’t have to be on your own,” from ”A Message,” is typical). Combined with arrangements that aim to uplift, the results can be sublime — panoramic tracks like ”Talk” and ”Low,” which throb in a new, almost clubby way for them. ”The Hardest Part” is imbued with the sense of regret and letting go that we’ve heard from the band before, but with added musical muscle.

Yet Coldplay can also sound a little lost in space. They’re clearly trying very hard to grow, but sometimes all they have to show for it are tracks that require road maps. ”Square One” starts all New Agey, shifts to an electronica-lite pulse, jacks up the arena-techno à la U2’s Pop, then closes softly and acoustically. (This isn’t the first time on this album the flawed Pop comes to mind.) But somewhere along the way, the melody and emotion are submerged. Their ballads also suffer from overinflated arrangements: Almost a parody of sensitivity, ”Fix You” is one big marshmallow, outdone by the recent singles from Keane, the latest (and most emotive) in that never-ending stream of Coldplay mimics.

By the end of the album, you long for a little more of the gorgeous directness and simplicity of ”Trouble” or ”The Scientist” (or even some ”Yellow”-like riffing). A hidden final track, ”’Til Kingdom Come,” is a knockin’-on-heaven’s-door strummer written for Johnny Cash, which feels more like what it is — a faux-Cash song — than a genuine Coldplay tune. The fact that Coldplay are trying anything is, of course, admirable. You can’t help but respect a band that wishes rock were back on the compassionate tip, and doesn’t pander along the way. But as Martin himself sang last time around, nobody said it was easy.