Beethoven

Before him a symphony was something written for a court or a church; after him it was a way for one person to address the world. Beethoven was the finest pianist in Vienna in his twenties, began losing his hearing around thirty, and in 1802 wrote the Heiligenstadt letter to his brothers saying he had nearly ended his life — then wrote the Eroica.

Listen for what he does with a motif. The four notes that open the Fifth are taken apart, transposed and restacked across all four movements, and the whole symphony grows out of them. Building the largest possible structure from the smallest possible material is his most useful lesson to everyone who came after. The late quartets go further still; almost nobody understood them at the time, and they remain the hardest place in Western music to reach.