The Piano Sonata No. 14 in C-sharp minor, marked Quasi una fantasia, Op. 27, No. 2, is a piano sonata by Ludwig van Beethoven. It was completed in 1801 and dedicated in 1802 to his pupil Countess Giulietta Guicciardi. The popular name Moonlight Sonata goes back to a critic's remark after Beethoven's death.
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