Paul McCartney appeared on NBC's Today yesterday (July 25th) and spoke with Al Roker about his upcoming children's book, Hey Grandude!, as well as his long and storied career. The animated book -- written by McCartney with illustrations by Kathryn Durst -- is due out on September 5th via Random House Books for Young Readers.

Among other things, McCartney revealed that due to the sheer number of songs he's written -- the majority of which he hasn't performed in decades, if at all -- he needs to re-learn his old songs before each tour: "(Paul McCartney): I have to re-learn everything I've ever written an awful lot. So, you can't retain them all. We go into rehearsal and I learn them, y'know? 'Oh yeah -- that's how it goes' (laughs). (Al Roker): Well, sometimes when you're re-learning them, do you kind of look and go, 'Y'know, this is pretty good'? (McCartney): I do. I really do. Y'know, that's one of the joys of doing some of the old songs, I say, 'Oh, that's clever. I wouldn't have done that.'"

AUDIO: TODAY - PAUL MCCARTNEY ON RE-LEARNING HIS SONGS