In his too-short life, Marc Bolan conjured the future with songwriting full of playful grooves, cheeky wordplay, and cosmic spirituality. His ’60s forays into psychedelic rock with his early band John’s Children (“Desdemona”) transitioned first into freaky folk and then into crunchy glam (T. Rex’s 1973 classic “20th Century Boy”). Countless artists have channeled Bolan’s swagger, led by The Power Station’s cover of “Get It On (Bang a Gong).”