Listen to FULL CIRCLE SONG by Gene Clark.
Oren gave me a copy of "Musicophilia" by Oliver Sacks a few weeks ago. I highly recommend it. I'll steal a blurb so I don't have to describe it:
"Musicophilia: Tales of Music and the Brain" examines the extreme effects of music on the human brain and how lives can be utterly transformed by the simplest of harmonies. With clinical studies covering the tragic (individuals afflicted by an inability to connect with any melody) and triumphant (Alzheimer's patients who find order and comfort through music), Sacks provides an erudite look at the notion that humans are truly a "musical species."
The consistently interesting thing about the book is how there are musical parts of the brain that can keep working when every other part of the brain doesn't, like the Parkinson's patients who can't will themselves to move but can get around freely when they hear a song.
Sacks also discusses how people can retain songs over a lifetime and recall them fully and completely under certain circumstances, even when they're senile. Not really surprising, but I do have a minor anecdote. The other day, I was riding the subway, listening to a different song, when all of a sudden the Full Circle Song started playing in my head. And it was so overwhelmingly moving, I can hardly tell you. I had to go home that night and find it on iTunes so I could listen to it a few times in a row. Strange, because I had only listened to it maybe three times in three years (and have never had the Byrds reunion album it's on also), and hadn't really identified it as a favorite -- I didn't even know I knew the melody. But I have now.