From the first seconds of Amir Bar-Lev’s extraordinary documentary Long Strange Trip, the viewer is reminded of the vast breadth of music created by the Grateful Dead over their three-decade run. The first tune heard, “Death Don’t Have No Mercy,” recorded at the Fillmore West in San Francisco in February 1969, and issued on side four of the Live/Dead album later that year, may not be the first tune you’d think of when considering the Dead. But hearing it again, in this context, one is struck by just how perfectly it encapsulates their genius: Alternately tender and brash, this simple blues showcases the singularity of Jerry Garcia’s guitar and vocal work, and the intuitiveness and dynamism of the group as a whole. Throughout this two-disc set—three if you purchase it through Amazon (it’s also available in digital, with LPs to follow)—on both familiar studio recordings (“Uncle John’s Band,” “Touch of Grey”), canonic live performances (several tracks from the recently issued Cornell ‘77, the 2/14/70 ultimate “Dark Star”) and a handful of previously unreleased surprises (“China Cat Sunflower/I Know You Rider,” from France 1971; a tasty “The Music Never Stopped” from ‘75), those reminders arrive over and over. It’s not that you don’t know already—with thousands of hours official and nonofficial to access—that the Dead were capable of going to so many different places so naturally. But grooving along to what could be anyone’s random playlist—an acoustic “Dark Hollow” leads to a stellar “Stella Blue” and that Nassau Coliseum “Althea” is as special as Al Franken insists in the film—substantiates one of the most salient points of Long Strange Trip. Whatever flaws there were, there is a bottomless well of joyous, uplifting pleasure and treasure in what these musicians left behind.