I sing all the time. I am not good at it, but it just explodes out of my mouth sometimes. Yesterday I went into the bathroom here at work (there are 2 stalls in there), and I was in one singing "You're the cutest thing I ever did seeeee....I really love your peaches wanna shake your tree"...and I realized that sometime during the chorus a lady walked in and was in the stall next to me...I started laughing and said (while still in my own stall), "Sorry, I just can't help it...the acoustics in here are so good".
She said nothing.
I giggled all the way out the door.