SPECTRUM ROAD Jack Bruce and friends pay tribute to one of fusion’s founding fathers    The word “supergroup” gets tossed around a lot, but Spectrum Road makes an impressive case for itself. Each member of the quartet comes with a wildly impressive résumé. Guitarist Vernon Reid is the prime mover behind Living Colour, the juggernaut that helped define rock-funk in the ’80s. Keyboardist John Medeski, one-third of Medeski Martin &...