Wow, what nice stuff to wake up to!
I have no luck finding old threads; I did think before hitting BS but life is about choices.
Not singing when not happy - It sure is an indicator. I lost it during the four years after I was environmentally poisoned ('99) and before I de-toxed to recover. Noticed only when it started to come back but it only really came back in Feb when I rediscovered old friends and started listening to music again. Feeling happier = singing more.

Have also noted "theme songs". Living in Edmonton, Alberta, I kept singing, "I wanta go home" and others on that theme. Tired of moving: "Nail your shoes to the kitchen floor..."

Though, often as not, if someone asks, "What was that song?" I look blank and have no idea what I was just singing. When I segued from a friend's rock song to Let It Be, that stopped me in my tracks. (In the middle of a parking lot - but this is Whidbey)

Allison - how 'bout a bumper sticker: Caution Driver NOT Singing." I'm sure that happier drivers are better. But yours might get others singing!   

Jacqui: Hope you get out on that beach and SING!

Reading The Horse Boy yesterday. In the night, a lone horseman went by the camp singing and the Mongolian guide sang back to him - assurance in the night! The next day, the driver sang as they travelled.

So, maybe we could all sing more and a little louder. Isn't there an old song about getting the whole world to sing? It causes us to breathe better and feel better; it could improve the world. Singing people are happier people - and they seem to make others happier also.