The high profile of Sigur Ros and Mum (playing in Tokyo next month) make the Fat Cat label look like a haven for atmospheric Icelandic bands. But the label has made its name not so much for a sound, but for intriguing sounds. That, more than anything, is why its new compilation, "Branches and Routes," is so difficult to pin down.

Fat Cat ascribes to a genre-free ethos, which means that the record encompasses everything from David Grubbs' avant-garde, acoustic songs, to Xinlisupreme's smashing, symphonic barrage of noise. It is literally the quality of the sounds themselves, the way the various artists arrange, twist or contort their chosen sonic palette that sets the record, and hence the label, apart.

While Sigur Ros' "Eg Mun Leknaest" favors big brushstrokes of lush distortion, Team Doyobi's track, "E5," pushes in another direction entirely, coupling the throb of industrial pistons with spluttering beats and ghostly diva-esque vocals. Sylvain Chaveau's delicate piano work has been compared to Yann Tierson, while sometime Bjork collaborator Matmos puts disco through the wringer.

The catch here is that an unusual sound is not interesting unto itself. The Dylan Group's cut, "Avila," for example, begins with an enticing rhythmic melody played on bells, but leaves the listener wishing someone else would sample it for a proper song.

For the most part, Fat Cat artists manages to exploit their bleeps and booms well. Forget about melody or a distinct style. "Branches and Routes," while a record of Fat Cat's growth from obscure London record store to important postrock and electronica indie label, is also a primer of the possibilities of sound.