The follow-up to the introductory package 1-3, 4 is the album that established the Norwegian quartet Supersilent as an up-and-coming free improv artist, drawing much attention from the magazine The Wire, especially. When all young artists were either drawn to lowercase or atmospheric experimental electro, the quartet dived into burning-hot free improvisation, blending jazz, rock, and electronica idioms with a distinctive Scandinavian touch -- something in the use of space and the field recordings that evokes the mountains, snow, and fjords of Norway. As usual, the tracks are numbered instead of titled as to obliterate any preconceptions. "4.1" begins atmospherically before the drummer starts rolling and pounding. But this introduction comes to an abrupt end and almost feels like a false start, a warm-up. "4.2" is also mostly atmospheric, but now the E-Bowed electric guitar is more prominently featured, along with treated voice samples. Drums escalate, synthesizers build tension, and the sonic battle has begun. An intentionally sloppier incarnation of Steamboat Switzerland could have recorded "4.3." The album's highlight resides in "4.6," a long improvisation with many twists, turns, and shifts in dynamics and moods. 4 shows Supersilent exploring an unheard-of fusion of free styles, sculpting their own niche. Recommended.