In the fall of 1784, Mozart and his wife moved into an elegant apartment near St. Stephen's Cathedral in Vienna. The house belonged to the Camesina brothers, whose father made ornamental rococo plasterwork, and the ceiling of one of the larger apartments in the house was decorated in a lavish style as a kind of show room for prospective clients.

In that apartment on today's date in 1785, Haydn heard a few of the new string quartets Mozart had recently completed and would eventually dedicate to the older composer. It's likely that Mozart himself performed the viola part on that occasion.

A month later, when Mozart's father paid a visit to Vienna, the rest of the new quartets were performed, again with Haydn present. That was the occasion that Haydn turned to Mozart’s father and said: "Before God and as an honest man, I tell you that your son is the greatest composer known to me either in person or by name."

It was probably the most deeply appreciated compliment Mozart ever received, but one the following evening wasn't too shabby either. After a performance of one of his Piano Concertos, his majesty the Austrian emperor waved to Wolfgang as he left the stage and called out: "Bravo, Mozart!"