Almost thirty years after they first met at a Bill Monroe concert in West Grove, Pennsylvania, David Grisman and Jerry Garcia collaborated on an eponymous duet album. Of course, Garcia and Grisman had played together in countless groups over the years, and by the time they met up at Grisman’s home studio in early 1991, their interpersonal chemistry had long been nurtured. These acoustic recordings exhibit a high level of technical expertise and deeply wrought musicianship, but more importantly, they emanate the kind of affection that can only grow from two friends playing together. Bluegrass is the root music here, but the songs adapt to all kinds of forms. There is reconfigured blues in a reading of B.B. King’s “The Thrill Is Gone” and traditional folk music in “Walkin’ Boss.” Two of the album’s best moments come from pages of the Great American Songbook: a lazy, lonely take on Hoagy Carmichael’s “Rockin’ Chair” and a shuffling version of Irving Berlin’s “Russian Lullaby.” While the duo has an amazing ability to reinvent standards, the Middle Eastern-themed “Arabia” shows them cutting loose like gypsies around a desert campfire.