On December 24, 1781, Austrian Emperor Joseph II had two celebrated keyboard players in his Vienna palace and he couldn’t resist setting them against each other in an unusual competition. This is what Mozart wrote to his father about the contest that pitted him against Muzio Clementi:
A word about Clementi. He’s a first-rate harpsichord player, period. He has a very nimble right hand. His strong suit is thirds. But aside from that he doesn’t have a penny’s worth of taste or sensitivity. He’s a mere mechanic.
After we had spent enough time on the formalities, the Emperor declared that Clementi should begin. “La Santa Chiesa Catolica,” he said since Clementi is a Roman. He improvised and then played a sonata. Then the Emperor turned to me. “All right, have at it.” I improvised and played variations. The Grand Duchess came up with some sonatas by Paisiello, scribbled out in his own handwriting, of which I had to play the Allegros and Clementi the Andantes and Rondos. Then we picked out a theme from them and developed it on two pianofortes.
Strange to say, even though I had borrowed Countess Thun’s pianoforte, I played it only when I played alone. That’s what the Emperor wanted, and by the way, the other instrument was out of tune and three keys were stuck. “That doesn’t matter,” said the Emperor. Well, I made the most of the situation, assuming that the Emperor knew my skill and my knowledge of music and just wanted to show a special courtesy to a foreigner. Anyway, I have it on good authority that he was quite pleased with me. He was very gracious and said a good deal to me in private, and even mentioned my marriage.
The Christmas Eve keyboard contest between Mozart and Clementi is the first two-piano performance on record.