Claude Debussy was admitted to the Conservatoire de Paris at age 10. By age 12 he had won a major prize for playing a difficult Chopin piece. Shortly after that, he began to compose his own works, winning the prestigious Prix de Rome. His career just went up from there. Called the first Impressionist composer, he never liked the label, but his style does seem to fit it.
He sat for this portrait by Jacque-Emile Blanche: