Every Number One song ever written is only made up from bits from other songs. There is no lost chord. No changes untried. No extra notes to the scale or hidden beats to the bar. There is no point in searching for originality. In the past, most writers of songs spent months in their lonely rooms strumming their guitars or bands in rehearsals have ground their way through endless riffs before arriving at the song that takes them to the very top. Of course, most of them would be mortally upset to be told that all they were doing was leaving it to chance before they stumbled across the tried and tested.