Xavier was small in stature, of slight build and a somewhat pale complexion, and he almost always looked serious, even austere. The public was struck, at times intimidated, by his appearance. Two years earlier, at Frankfurt am Main, Johann Wolfgang von Goethe, who was fourteen at the time, had attended a concert given by the Mozart children. Little Xavier was aware of his celebrity and of the power that his musical talent gave him over the public. He already was familiar with the art of seducing and dominating an audience by the age of fifteen.