Noah and the Whale have unexpectedly transformed themselves from lightweights known for a novelty hit to a band attracting serious consideration. This time last year, they were frolicking in the video for the twee top 10 single 5 Years Time; now, there is near-unanimous acclaim for their new album, The First Days of Spring, and their two ICA shows, in front of quietly rapt audiences, are sold out.

If sonorous frontman Charlie Fink hadn't been left by his girlfriend Laura Marling, who was once in the band, none of this would be happening. Poleaxed by depression, Fink wrote an album about it, and the result is so bleak and full of sorrow that it's surprising he can bring himself to perform it in public. He carried it off by making the show feel like a eulogy for the relationship: the lights were dim, the mood sombre and the music stately. Fink's singing voice can uncharitably be described as deadpan, but tonight there were cracks that suggested time hasn't been much of a healer.

But it wasn't the words he sang (standard post-breakup wistfulness epitomised by "I need your life in my life/ So come back to me, my darling") that gave the show its punch, so much as the way he, and the other Whales, gave the music room to breathe. Fink's guitar and Tom Hobden's violin were the predominant instruments, sketching out each song slowly and sparingly. Some, such as Love of an Orchestra ("The most requested song in our request box," said Fink), were dramatic, while others, like Stranger ("Last night was the first time I'd slept with a stranger since you'd gone"), were parched and sad, yet always touching.

The spell was broken by the jolly 5 Years Time, and then they were gone – basking, perhaps, in the knowledge they've pulled off one of 2009's most remarkable reinventions.

At the Sage, Gateshead on 27 September. Box office: 0191-443 4661. Then touring.