There are two sides to this coin (think karaoke at midnight) but the part that I love and would like to emphasize is that it is perfectly acceptable to sing out loud almost anywhere. One time I was riding along on a jeepney when suddenly the guy sitting across from me burst out into song. Loudly. I was the only one who looked twice.
Many times I've been shopping in a store and a sales person in the same aisle as me suddenly chimes in with the music playing on the loud speaker system. They have no qualms about that at all.
I decided to experiment with this. I was curious what people would do if a foreigner, who already sticks out like a sore thumb, burst out into song in the grocery store. The answer? Nothing! They didn't even look twice. I love that! Now I don't have to feel weird about humming along to the radio or singing a song of my own.
Now, isn't that refreshing? Who cares what other people think? Enjoy life a little! If your heart feels like singing, then sing! We should all learn a lesson from the Filipinos on this one.
You may be wondering what happens if the person who is singing along can't carry a tune. Nothing. They are welcome to sing too (think karaoke at midnight). :D