What is "natural horn"

The natural horn is a musical instrument that is the ancestor of the modern-day horn, and is differentiated by its lack of valves. It consists of a mouthpiece, some long coiled tubing, and a large flared bell. Pitch changes are made through a few techniques:

• Modulating the lip tension as done with modern brass instruments. This allows for notes in the harmonic series to be played.
• Changing the length of the instrument by switching the crooks. This is a rather slow process. Before the advent of the modern valved horn many ideas were attempted to speed up the process of changing the key of the instrument.
• Changing the position of the hand in the bell; this is called hand-stopping.

This instrument was used extensively until the emergence of the valved horn in the early 19th century.