Chris Thile & Brad Mehldau: Chris Thile & Brad Mehldau

If you blinked at the wrong time, it was easy to miss the fact that Chris Thile and Brad Mehldau had played together at all. For two such restless collaborators, each occasional encounter was one more fleeting meet-up among many others—a quick one-off in 2011, a nine-city string of duo shows in 2013 and another two-night live stand after a couple years more. That last was accompanied by a quick stop in the studio to finally give the rest of us a more lasting taste of what was going on. The mandolin/piano pairing makes for a beautifully eclectic experience on this hour-long set, spread over two CDs for reasons unclear.

You could oversimplify by saying that Mehldau is mainly a jazz player while Thile is more rooted in bluegrass, but these fellows treat such distinctions as an irrelevant nuisance anyway. "The Old Shade Tree" (the lone co-written original here) kicks things off with a minor mid-tempo bounce that smoothly encompasses both. Rollicking piano cascades and frisky chop-strumming sound like the most natural of partners, while Thile's vocal capering reminds us yet again that he's much more than 'just' a virtuoso player.

Beyond those primary components, their palette has just as much room for down-home country or ragtime, contemporary folk and a lovely Celtic air to close things out. Each contributes two more new songs to the roster individually, ranging from the twistingly intricate excursion of "The Watcher" to the simpler groove and chorus of "Noise Machine." Thile's extensive centerpiece "Daughter of Eve" manages to span several of those elements and still make space for a dreamy almost-classical interlude. As always, the duo is equally at home reinventing other material, evocatively exploring the lilting wistfulness of Joni Mitchell or the jaunty chordings of Elliott Smith.

The affair is a vivid and fruitful meeting of minds that allows for dazzling tight interplay and delightful improv alike. Even a too-brief set can pack plenty of surprise. Fans of either artist doubtlessly are already set to come with open ears and unlikely to be disappointed; after all, it's friction among such different basic elements that often sets off the more colorful sparks.