When Norman Rockwell set out to write his 1960 memoir "My Adventures as an Illustrator," he began by talking into a dictaphone recorder with his son Thomas. The soundtrack of this video is an excerpt of that audio.
Then he talks about the many adjustments he was making to the painting. The audio gives a sense of how conscientious Rockwell was about even the smallest details, and it also reveals how much he sought other peoples' judgment and approval.
"I put the red bandana or the effect of red on the son of the Indian...."
"Tomorrow I'll get to work on the pirate and his Spanish girlfriend and make all of her sort of a greenish, grayish, bluish sort of a haze. She's kind of the mystery woman of the whole thing. Don't you think that green on her is awful good, with the bright red lips?"
"And I took (psychologist Erik) Erikson's suggestion and I'm going to have gray, sort of opaque gray eyes on the pirate, coal gray eyes, and his hair is brown, and so that leaves the Spanish girl with the black for sure. The black will skip from the Spanish girl up to the pirate's son, and there will be no black on the pirate at all.
Rockwell devotes an entire chapter in his book, My Adventures as an Illustrator to a case history of the changes the painting went through.
The Norman Rockwell Museum's page about their audio archive. If you go to the museum, they'll let you listen to the raw audio. I've tried sampling some of it, and Rockwell tells a lot of stories that aren't in his book.