This composer said, "the devil may play it" about his difficult Wanderer Fantasy, which he couldn't play himself.
This composer said, "the devil may play it" about his difficult Wanderer Fantasy, which he couldn't play himself. He wrote the incidental music to a Helmina von Chezy play containing a shepherd's song, Rosamunde.  Another work begins with two Gs being played in triplets and describes an evil elf who kills a boy, Der Erlkonig.  This composer abandoned a symphony after finishing only two of its movements and created a variation on an earlier work of his, "Die Forelle." For 10 points, name this composer of the "Unfinished" Symphony and the Trout Quintet.
This composer said, "the devil may play it" about his difficult Wanderer Fantasy, which he couldn't play himself.
Franz Schubert  (NOTE TO READER: Do not reveal the alternative answer to the first or second part of the bonus unless necessary.)