Part of a general nostalgia boom, post-Woodstock, including newfound interest in old time radio shows and films like Casablanca and the Marx Brothers oeuvre. WCBS-FM in New York became the first oldies station, playing doo-wop, Elvis, etc. Pre-Beatles artists were touring before unthinkably-large audiences. Rick Nelson's 70s hit "Garden Party" was about the nasty reception his country-rock band got at Madison Square Garden, by a crowd that was expecting 1950s Ricky.