This is what lingers with actor and filmmaker James Keach from Glen Campbell's final recording session in 2013, capturing the song "I'm Not Gonna Miss You."
"I had my cameras in there," Keach said. "Sometimes Glen would stop and say, 'I'm so sorry. I can't remember.' The interesting thing to me is that sometimes he would forget the words, but he never forgot the music. He would always hit the notes."