When bassist Edgar Meyer and mandolin player Chris Thile began performing together in 2003, only one half of the duo had been deemed a "genius" by the MacArthur Foundation. But exactly a decade after Meyer, Thile was also awarded the prestigious prize -- and during those ten years, the pair's collaboration grew from sporadic stage-mates to more-than-occasional musical partners.

In 2008, Meyer and Thile released a self-titled album of duets -- an album that explored both the soaringly harmonious and the sharply angular elements of combining the two instruments together. Two years later the pair was joined by cellist Yo-Yo Ma and fiddler Stuart Duncan on the acclaimed Goat Rodeo Sessions album that won a Grammy Award for Best Folk Album. And although the two haven't made a duet record together in five years, their work together has continued behind the scenes -- Meyer produced Thile's Sonatas and Partitas album of Bach works originally for solo violin, and made a guest appearance on Nickel Creek's reunion record, A Dotted Line. 

Although Thile grew up idolizing Meyer -- particularly his 1997 album with Béla Fleck and Mike Marshall, called Uncommon Rituals -- it's apparent from their latest pairing that their relationship has grown from one of mentor and mentee to one of musical equals. Bass & Mandolin features a constant give and take between melody and accompaniment -- as Meyer bows the melody on tracks like "Monkey Actually" and "The Auld Beagle," Thile flits around him in accompaniment, only to quickly swap places or join in in an ecstatic breakdown. 

Also in a first for the duo, the album occasionally features Meyer and Thile not on bass and mandolin but on piano and guitar -- most notably on "I'll Remember For You," a contemplative and occasionally dark piece whose title gives an indication of the weighty emotion behind the song.

More than anything, it's easy to hear how much fun these two have playing together. Both of the duo's albums are filled with songs flavored by a back-and-forth, bet-you-can't-catch-me playfulness and humor that can only come of the tightest musical relationships. On Bass & Mandolin, that relationship is a little older and a little wiser -- and sounds all the more comfortable and relaxed for it.