SPECTRUM ROAD Spectrum Road [Palmetto] “Supergroup” is a term that was long ago diluted, but every once in a while the stars align and the word regains its meaning. Spectrum Road is incontestably a supergroup: Cream bassist Jack Bruce; Living Colour guitarist Vernon Reid; keyboardist John Medeski of Medeski Martin & Wood; and drummer Cindy Blackman, who has backed husband Carlos Santana, Lenny Kravitz and others. Spectrum Road—and the quartet’s...