God, I love drunk people.
There's one particular stretch of the Central Line where you can't hear anyone talk. You have to shout at your mates and even then they won't understand you. We had no problem hearing her sing. She was a tiny thing and I, standing a mere two feet away, was shocked by the physical power of her voice. It was incredible. I could feel the projection from it. After a bit of singing, everyone started clapping and made their way down to our end of the car.
She became embarrassed because she was drunk and sang off key (like I could tell), but we convinced her to sing more. She pulled out a tuning fork, tapped it and listened intently. Then she opened her mouth and graced us with Tosca all the way back to Ealing Broadway.