What a remarkable document this is. In late 1962, a 20-year-old banjo player and guitarist named Jerry Garcia, along with four other acoustic musicians, entered the studio of Stanford University’s radio station KZSU, in Palo Alto, Calif. One of those other fellows, named Bob Hunter, played upright bass. Another, David Nelson, played guitar. The three of them sang and, together, with Dobro player Norm Van Maastricht and multi-instrumentalist Ken Frankel, they called themselves the Hart Valley Drifters. The recording of their set—mostly filled with traditional bluegrass numbers—languished for nearly 50 years. Now, discovered and cleaned up, it’s finally out, giving us access to the earliest known music of Garcia (as well as future Grateful Dead lyricist Hunter and New Riders founder Nelson). Historical value aside, it’s an exciting collection—Garcia was already a remarkably facile player and nuanced vocalist. His lead vocal on “Pig in a Pen,” a trad number that would become a staple of his short-lived bluegrass side-project Old and in the Way, a decade-plus later, contained all of the warmth and command he would fine-tune with more experience. And the picking, too, is superb: “Cripple Creek,” an instrumental breakdown, barely lasts a minute and a half, but both Garcia’s banjo and the guitar-playing are equal to that of any major folk festival habitués of the time. There are harmony-rich ballads, gospel celebrations and retooled blues—one of which, Walter Jacobs Vinson and Lonnie Carter’s “Sitting on Top of the World,” closes the program—would surface five years later on the Dead’s debut as a blasting electric rocker. Here, with Garcia switching to guitar, it’s tender and spare, reminiscent of the style the Dead would use in their acoustic sets of 1969-70. This music offers only scant hints of what was to come, but that’s OK; as a stand-alone, it’s a thing of beauty.