Have you ever woken up singing/humming a song? I mean literally, as you woke from a deep REM sleep and as you slipped back into consciousness, a tune was already playing in your head and you were mouthing the lyrics?
Well, it happens to me. A lot. I don't know exactly when it started happening, but it definitely started sometime after I entered my twenties (~ nine years ago.)
Some days, the genre varies, I have woken up singing everything from Nine Inch Nails, to Johnny Cash, to Run D.M.C., to gospel hymns. It's wacky crazy.
And I don't think that anything really triggers the singing. Nothing from the previous day/night, any media influences, or any dreams that I've had. I just wake up singing random songs. And then for the rest of the day, the song's stuck in my head and all I do is think about/sing the song.
I'm a HUGE music junkie. At one point, I had more than 4,000 mp3 files on my old desktop...that I actually PAID for. If it weren't for a bad virus wiping out my hard drive...and me NOT backing up my data, I would've still had those files...and I prolly would have closer to 10,000 files today. Oh well, you live and you learn.
I'm sooo into music that I sometimes wonder if I missed my calling somehow. Please refer to #13, here.