When Mozart met Beethoven

A 17-year-old Beethoven plays for the respected composer
Paul Allais, 'Beethoven with Mozart' (Details)
From Otto Jahn's Mozart, quoted in Michael Hamburger's Beethoven: Letters, Journals and Conversations:
Beethoven, who as a very promising young man came to Vienna in the spring of 1787, but had to return home (to Bonn) after a brief stay, was taken to see Mozart, who asked him to play something. Mozart, thinking that he was listening to some studied show-piece, praised it rather coolly. Beethoven, who noticed this, asked Mozart for a theme suitable for improvised variations. As he always played excellently when excited and, at this moment, was also inspired by the presence of a master whom he respected greatly, Beethoven began to perform the piano in such a manner that Mozart, whose attention increased to the point of fascination, at last went quietly to his friends sitting in the next room and said emphatically: "Keep your eyes on that fellow; one day he'll give the world something to talk about."