Page and Robert Plant were also grounded in British folk music and fascinated by mythology, Middle Earth fantasy, and the occult, as became increasingly evident from the band's later albums (the fourth LP's title is comprised of four runic characters). A song that builds from a folk-baroque acoustic setting to screaming heavy metal, "Stairway to Heaven," fittingly became the best-known Led Zeppelin song and a staple of FM airplay, although like most of the group's "hits," it was never released as a single. Though sometimes critically derided during their lifespan, Led Zeppelin was unquestionably one of the most enduring bands in rock history, with U.S. sales of more than 100 million records. When the Yardbirds fell apart in the summer of 1968, Page was left with rights to the group's name and a string of concert obligations. He enlisted John Paul Jones, who had done session work with the Rolling Stones, Herman's Hermits, Lulu, Dusty Springfield, and Shirley Bassey. Page and Jones had first met, jammed together, and discussed forming a group when both were hired to back Donovan on his Hurdy Gurdy Man LP.