“Arthur Rubinstein was standing in the lobby of a concert hall proudly watching the audience filing in to hear one of his recitals. Finally, when the last one had gone in, Rubinstein made a move to enter. An usher blocked his way. ‘Sold out, mister’, he said, and to reinforce his words he pointed to a sign beside the box office announcing just that. Rubinstein smiled, ‘Sold out, I know,’ he said, and made another move. ‘You don’t understand,’ said the usher. ‘There ain’t no seats left. We can’t seat you.’ And Rubinstein replied: ‘May I be seated at the piano?’
Cited in Kelly, Henry & Foley, John (1998) Classic FM Musical Anecdotes. London: Hodder & Stoughton, p. 98.