The sixth and latest by Sigur Rós lacks the fundamental essence that has made the Icelandic post-rockers one of the most well-respected bands in indie circles.

Where is the heart, the vigor, the verve?

Nearly an hour long, Valtari is missing the visceral influences that helped establish their name. It's beautiful, in that Sigur Rós way of ethereal twinkling and heavenly dreaminess. Yet, there's none of the rougher side of Sigur Rós, the part with crescendos and crashing drums, the part that not only struck your aesthetic interests, but also your heart.

The title track is a sleepy example that looms and lurks in your ear — a collection of brooding, slowly building analog and digital noises, a project in ethereal ominousness. But what does it accomplish other than sounding darkly pretty? Not much, and it begins to drag without the aid of drums to inject liveliness into its dusky grace. "Varúð" is the only track on the album with a satisfactory climax, and fortunately it's an excellent one marked by an angelic choir presiding over thunderstorm rhythms and apocalyptic guitarwork.

Pretty, but a little too safe, Valtari combines the soporific elements of the group's 2002 album, ( ), with the child-like delicacy of 2002's Finally We Are No One by fellow Icelandic alt-rockers Mum. Without a payoff, the foursome's first album in four years tends to wear on you. The fifth track, "Dauðalogn," roughly translates into an English phrase that encapsulates the album: "calm death."

2 out of 5 stars

(Out now on Parlophone)