Details: The invention of the chromatic pedal, which simplified playing, significantly increased the popularity of the harp. So popular did the instrument become that Beethoven wrote his Variations on a Swiss Song 'pour harpe ou piano'. Later, his most popular pieces were arranged, such as the 'Moonlight' Sonata, which was virtuosically transcribed by John Thomas, harpist to Queen Victoria. The Divertissements pour la harpe were once thought to be by Beethoven but are possibly by his contemporary and acquaintance, Count Karl Wilhelm von Haugwitz. Leading Italian harpist Paola Perrucci plays on an erard harp except for the Adagio grazioso, Op. 31, No. 1 where she plays on a modern instrument.