Breaking out in song while in one's cups is perhaps a distinctly British custom because in my life I've only experienced it once in America.
It was in the late 90's in San Francisco. The remake of "Killing Me Softly" was at the top of the pop charts. I was visiting with an out of town friend, who had never seen S.F. After doing requisite sightseeing during the day, we caroused at night.
The last night we were there, it was nearing closing time at the bar we were in. (Don't ask me the name, I never remember such things. After all a bar's a bar.)
The DJ played one last song. It was "Killing Me Softly". The crowd erupted and leapt to their feet. We spontaneously joined together swaying along with strangers singing "our lives" with our words at the top of our lungs. Nothing else existed for those three minutes. The magical concoction of the hour, the libations and the song took us all to a place of eternal brotherhood. A perfect moment.
The hair still stands up on my neck when I hear that song.