Although "Sgt. Pepper" was preceded by several albums that had begun to bridge the line between "disposable" pop and "serious" rock, it successfully gave an established "commercial" voice to an alternative youth culture and marked the point at which the LP record emerged as a creative format whose importance was equal to or greater than that of the single. Bill Bruford, a veteran of several progressive rock bands, said that "Sgt. Pepper" transformed both musicians' ideas of what was possible and audiences' ideas of what was acceptable in music. He believed that: "Without the Beatles, or someone else who had done what the Beatles did, it is fair to assume that there would have been no progressive rock." In the aftermath of "Sgt. Pepper", magazines such as "Melody Maker" drew a sharp line between "pop" and "rock', thus eliminating the "roll" from "rock and roll" (which now refers to the 1950s style). The only artists who remained "rock" would be those who were considered at the vanguard of compositional forms, far from "radio friendly" standards, as Americans increasingly used the adjective "progressive" for groups like Jethro Tull, Family, East of Eden, Van der Graaf Generator and King Crimson.