Vocals on more abstract works can be difficult, for me it seems that often they impose a kind of structural narrative that the music seems to actively in opposition to, so there's a clash or dissonance which doesn't seem to provoke anything for me. I think this on the other hand has something in the tonality of Sylvain's voice that really molds around what Fennesz does, and the sparseness of the electronics really gives the vocals space to fill in a really subtle way. Both have worked with Ryuichi Sakamoto too, I wonder if that's the connection that makes it work?