Nostalgia has long been the sound of the future. Popular music is largely a game of reassembling existing pieces in stylish and appealing ways, of crossing x with y with z in hopes of stumbling upon something fresh. Genuine innovations are rare, and even music that set off revolutions has often looked backward: punks reacting against the excess of prog and arena rock by fetishizing the raw simplicity of early rock 'n' roll, grunge fomenting under the influence of Zeppelin and Sabbath, Arcade Fire repurposing the stadium anthems of Springsteen and U2. As told by his brother Bobby, A Star Is Born's Jackson Maine summed it up like so: "Music is essentially 12 notes between any octave. Twelve notes, and the octave repeats. It's the same story, told over and over, forever. All any artist can offer the world is how they see those 12 notes."