Watch the moment Paul McCartney composed "Get Back"

In one of many magical moments in Peter Jackson's documentary The Beatles: Get Back, Paul McCartney writes "Get Back."

"We were sitting in the studio and we made it up out of thin air … we started to write words there and then … when we finished it, we recorded it at Apple Studios and made it into a song to roller-coast by," McCartney said in The Beatles Anthology.

And Mark points out that the below video is even better: "Ringo and George suddenly realizing Paul is onto something, Ringo claps a rhythm, and George starts playing along."