James Brown’s extensive catalog is rife with exotic oddities, but this one tops them all. Rescued from the original two-track master of an unreleased full-length album, These Are the J.B.’s documents the explosive entrance, in early 1970, of bassist Bootsy Collins and his guitar-slinging older brother Catfish into The J.B.’s orbit. It jumps off, almost literally, with the jazzy title cut, which encapsulates the fluid, hard-driving sense of rhythm that the Collins brothers would bring to “Sex Machine” and other staples. It’s followed by “I’ll Ze,” a funk-blues jam that features solos from each member of the group (including a sweetly chicken-picked break by Catfish). “The Grunt,” with its opening horn squeal famously sampled by Public Enemy, kicks things into overdrive, but “When You Feel It, Grunt If You Can”—a 12-minute funk clinic that opens as an instrumental cover of Marva Whitney’s “It’s My Thing”—really defines the session. Under Collins’ direction, the band switches gears in rapid fashion, calling out The Meters, Kool & The Gang and, eventually, Jimi Hendrix’s Band of Gypsys, whose “Power To Love” (known more informally as “Power Of Soul”) had only just been released. As a glimpse of funk history, not to mention the roots of Parliament-Funkadelic, this one is essential.