Copenhagen 10-piece Efterklang evoke a combination of Iceland's autistic-rockers Sigur Rós and the surgical assault of latter-period Aphex Twin. Mixing orchestral instruments, choir and electronic racket, Efterklang are a sonic revelation. Their name means reverberation, after all, and Tripper sounds like the echoes of music scraped off the walls of some centuries-old monastery that has witnessed the saints and the electric vacuum cleaners that cleaned up after them. A beautiful, literally breathtaking album, its nine tracks cover so much territory at such a dawdling pace it takes several listens to grasp everything. The glacial vocals of "Step Aside" are buffeted by plummeting drum and bass rhythms and wheezing pump organ; other songs recall Radiohead's frazzled sonic experiments, eventually emitting vocals as peaceful as a child's nursery rhyme. The sound of sweet teeth melting into old age.