One afternoon at a rehearsal in Carnegie Hall, it suddenly struck Arturo Toscanini that the score in front of him contained an incorrect note.
Over the years, neither he nor any other conductor had questioned the fidelity of the note, but at this particular moment, he became convinced that the composer must have had another note in mind. He asked an assistant to check with the music director of the Library of Congress, where the original score was stored.
The music director, in New York at the time, phoned Washington and had the passage hummed to him. He then phoned Toscanini's assistant and hummed the passage to the latter. The assistant dashed out on stage, signaled the orchestra to stop playing and hummed for the maestro. The note had indeed been incorrect. Toscanini, beaming, turned to the players and solemnly hummed the corrected version.