Once you get past the opening track, which is simply weird, this set is strangely engrossing. Brad Mehldau is, of course, one of the finest and most adventurous jazz pianists around. Chris Thile is a singer and virtuoso of the mandolin whose roots lie in bluegrass music. The purely instrumental numbers are at times quite mind-boggling in their cat-and-mouse interplay. Thile’s vocals can be a bit disconcerting in their falsetto moments but quite beautiful at others, as in the ballad I Cover the Waterfront. His vocal style may verge on the eccentric, but it’s perfectly in tune, and it soon becomes obvious that he and Mehldau are well matched in their musicality. Maybe it didn’t need a double album though.