I think Volker Bertelmann (Hauschka) is the kind of artist who likes to challenge himself. He's not content with his seemingly effortless ability to make albums full of beautiful and lapidary prepared piano pieces (Ferndorf), digressive travelogues (Foreign Landscapes), or transliterated dance music (Salon Des Amateurs), so he decided to collaborate on an album with American violinist Hilary Hahn. "Silfra" is the album, and it was 100% improvised in the studio (though they did practice and play together off-and-on for two years beforehand) and not retouched or overdubbed. There's something distinctly Oulipan about that--the setting of constraints in order to reach a different level of artistry."Clock Winder" (excerpted above) is a representative track from "Silfra". It still sounds like Hauschka, but halfway through there's Hahn's violin, a ribbon winding around the braided noises of the piano. This song, like most of the ones on the album, suggests something that is felt intensely, and it's hard not to imagine--and be envious of--the surprise and wonder these two musicians must have experienced while recording. Discovery, work, accident, chance, restraint. This is an album you can live with for a long time.[Buy Silfra]