Sir McCartney looked back on the Revolver album in a recent interview with Uncut, explaining that the success of "Eleanor Rigby" was a bit of a revelation to him. As a songwriter, it was one of the earliest times he tried building characters in his lyrics.
"It's quite a fun thing to do, to just dream up a name of a character and try and write that story of that character and then make it fit with another character," McCartney said. "'Eleanor Rigby,' I did it with just ... Father McKenzie and Eleanor. ... With my story songs, a lot of them besides 'Eleanor Rigby,' tend to be comedy. It's me doing the tongue-in-cheek thing, whereas 'Eleanor Rigby' was more serious. I think that's why it was more successful."
While Macca has a few more "story songs" laying around; they haven't been released because he ultimately doesn't think they're very good.
The documentary finds McCartney and producer Rick Rubin listening back and reacting to recordings from six decades of McCartney's music.