This anecdote has been attributed to the biography of young Johann Sebastian Bach.
One evening, Johann was playing his latest sonata to a German baroness at her estate. When he had finished, the baroness exclaimed with a bewildered delight: “Ah! Maestro! It was wonderful!… But what did you mean by it?" Bach promptly approached the keyboard again, and replayed the sonata. When he had finished, he turned to the baroness and explained: “That, dear madam, is what I meant.”