True to its title, this song does describe a rock concert. McCartney specifically wrote the song for his upcoming world tour, where he would perform in the US for the first time since 1966. Hence the references to "Madison Square" (Garden) and the "Hollywood Bowl." Another rock reference he got in was to Led Zeppelin guitarist Jimmy Page: "What's that he's rolling across the stage, it looks like the one used by Jimmy Page, like a relic from a different age." McCartney said he wasn't implying Page was a relic, but liked the image of the great vintage amp coming out for the show.
Ken - Louisville, KY