The Spectrum Road show at the Palace of Fine Arts in San Francisco on June 16 was intense Jack Bruce  Vernon Reid  John Medeski  and Cindy Blackman-Santana channeled something extraordinarily large  loud  dark  and beautiful—and even if Medeski hadn't been playing a Mellotron—which he was—it would still have been one of the heaviest progressive rock performances I've ever seen (the band's Tony Williams tribute origins notwithstanding)