Find the best cornet lessons, classes, and instructors at HeyKiki and learn how to play the cornet. The cornet is a brass musical instrument similar to the trumpet, with a mellower sound and more compact shape. It was developed by adding piston valves to the post horn, which allowed for more versatile play than the trumpet, which was slower to adopt the valve system. Modern trumpets, however, do have valves and can play the same music as cornets, though they differ in timbre. Ensembles that feature the cornet include brass bands, concert bands, fanfare orchestras, and jazz ensembles.