Every posthumous Hendrix release fleshes out the tale of his genius and changes the way you hear his music – changes the way you hear music, period. These two reissued (and beefed-up) live collections are no exception. The four-CD box Winterland is culled from six Jimi Hendrix Experience shows at San Francisco's Winterland Ballroom, recorded over three days in October 1968; Hendrix in the West (an expanded version of a 1974 release) gathers 11 gripping performances from West Coast shows in 1969 and 1970, the year of his death. They're essential listening: the sound of the greatest electric guitarist ever in glorious flight; the sound of psychedelic rock being invented, perfected and playfully taken apart; the sound of a world, and worldview, coming into being. The Winterland box is the more transfixing of the two, if only for the sheer amount of music (nearly five hours' worth) and the torrid force of Hendrix's soloing on songs like "Manic Depression" and the 15-minute-long "Tax Free," which tilts from acid rock toward the stormy grandeur of free jazz. Hendrix in the West isn't quite as overpowering, but there are mind-blowing moments: His "Johnny B. Goode" is a ripping tribute to (or is it a parody of?) early rock & roll, and "Little Wing" is Hendrix at his most lovely and lyrical. Not to be missed: the backstage interview on Disc Four of the Winterland set, a rare up-close-and-personal glimpse of Hendrix's intelligence, thirst for musical adventure and hippie-dippie charm. "What we're into now is history," Hendrix tells the interviewer. "We want to advance it." Mission accomplished.