Berlioz

He studied medicine and fled the dissecting room after a few months. He could not play any keyboard well enough to compose at one — only guitar and flute — which may be exactly why his imagination is not bounded by what a hand can reach.

The Symphonie fantastique dates from 1830, three years after Beethoven's death, and already belongs to a different century: five movements, a recurring idée fixe standing for the beloved, a fourth movement in which the protagonist dreams of his own execution, and a witches' sabbath to close. He also wrote the Treatise on Instrumentation, the first systematic orchestration textbook, which Wagner, Rimsky-Korsakov and Mahler all grew up on.