Like other complex pieces of machinery, musical instruments evolve and improve over time. In 1795, Anton Weidinger invented the equivalent of power steering for the trumpet. He created a trumpet with keys, so the player could play every note with ease, not just some of them. Weidinger also happened to be a colleague of Joseph Haydn's. The result of that confluence was Haydn's Trumpet Concerto in E-flat. We'll hear a performance by British trumpeter Alison Balsom, from a concert last month in Manchester, England.