Mozart once created quite a sensation in a theater he was visiting. It was at Marseilles. He had gone to the opera incognito to hear one of his own works performed. All went well till, in a certain passage, through some error in the copyist, the orchestra played "D" where Mozart had written "D sharp." This change of one note made a decided difference in the harmony, and turned the superior harmonic effect intended into a very ordinary sounding affair. No sooner was this done than Mozart sprang to his feet, crying out: " Play D sharp, will you; play D sharp, you wretches!" It may be imagined that such actions produced quite a sensation. The orchestra and singers stopped their performance and the audience began to hiss him down and cry, "Put him out!" and he was about to be summarily ejected from the theater, when he announced who he was. When it was known that it was Mozart, the tumult subsided, and cries of " Mozart! Mozart!" rang through the house. The very ones that were about to expel him now conducted him to the orchestra, and he was compelled to direct the opera, which was taken up anew. This time the missing D sharp was played in its proper place and produced the intended effect. At the close of the opera a perfect ovation was tendered the composer, and the people were not content until they had escorted him in triumph to his hotel.
From Anecdotes of Great Musicians by Willey Francis Gates