Jerry, you asked:
And how do you teach someone to write a song in a dream? Eat a large pepperoni pizza before you go to bed?
Actually, there are exercises you can do to train yourself to dream lucidly -- that is, that you know that you'r dreaming while you're dreaming, and can make deliberate actions that affect the outcome of the dream (such as turning around and asking the monster chasing you: "Why are you after me?" -- the monster will tell you, btw). I haven't used lucid dreaming to write a song, but I have used it to write poems and stories when the deadline was looming, and I've been stuck.
I don't write down my dreams when I wake up. Personally, I find the very act of fumbling for the pencil enough to make me forget the dream. Instead, I lay still in the bed and replay the dream backwards from the last scene I remember...
I did have one dream, back when I was a teenager, that gave me a line that I'd love to use in a song, someday, if I could figure out what to put around it without it becoming way too sacherine:
The scene: I'm struggling with my crutches (I have CP) to get up some steps and through a narrow door, when one of the people waiting for me inside the room calls out:
"Look! It's Peter Pan!"
to which I reply: "That's right! I can't walk, but I can fly!".
Well, if not a song, then maybe a sweatshirt slogan... ;-)