The Who perfected the rock opera, helped develop the revolutionary Marshall Stack and pioneered the use of synthesizers. Led Zeppelin's fusion of blues and folk music paved the way for hard rock. The Rolling Stones' innovation, showmanship and musical excellence, coupled with the songwriting team of Jagger and Richards, took rebellion to a new level. Their music soundtracked the lives of millions and heralded a new era of cultural significance, but they never once toured together. What if they h...