The natural horn is a musical instrument that was the earlier version of the modern French horn. It does not have valves, which makes it different from the French horn. Between the 17th and 18th centuries, the natural horn changed as it became different from the trumpet. This happened by making the bell larger and the tubes longer. The instrument has a mouthpiece, long coiled tubing, and a large flared bell. It was widely used until the early 19th century, when the valved horn was introduced.

Hand stopping technique

The natural horn has missing notes in its range of sounds. To play all musical notes, players need to adjust the instrument's key and use two methods: bending and hand-stopping. Bending a note is done by changing how the lips are shaped to slightly raise or lower the pitch. This helps fix the slightly off-pitch "wolf tones" that all brass instruments have. Hand-stopping is a method where a player places a cupped hand into the bell of the horn to change the pitch by up to a semitone (or sometimes slightly more). Both techniques also change the tone of the instrument.

Many people believe that hand-stopping began in the first half of the 18th century at the Dresden court with horn player Anton Hampel. Domnich (1807) said Hampel invented this method. He tried copying oboists who used cotton plugs to quiet their instruments and found that inserting a plug into his horn raised the pitch by a semitone. He realized he could play all notes smoothly by moving the plug in and out.

Pitch changes are made through these methods:
• Adjusting how tight the lips are, as done with modern brass instruments. This allows notes in the harmonic series to be played.
• Changing the instrument's length by using different crooks. This process was slow. Before modern valved horns, many ideas were tested to make key changes faster. Crooks were widely used by 1740.
• Moving the hand inside the bell, called hand-stopping. This lowers the pitch but makes the sound quieter.

Repertoire

The collection of music for the horn includes many pieces originally written for the natural horn. Before the invention of the modern horn in the early to mid-1800s, Western music used the natural horn and other natural brass instruments. Important composers who contributed to the horn's music include Handel, Haydn, Mozart, Beethoven, Telemann, Weber, Brahms, and others.

The ability of newer brass instruments to play all notes opened new opportunities for composers during the Romantic era, matching the artistic trends of that time. By the late 1800s and early 1900s, most music was written for the modern valved horn.

However, some composers still used the natural horn in their works. Brahms preferred the natural horn and wrote music for it. Benjamin Britten's Serenade for Tenor, Horn and Strings, although written for the modern horn, uses the F harmonic series. This piece has been performed with the natural horn to create a "sorrowful tone" because of its "fragile intonation."

György Ligeti's Hamburg Concerto uses the natural horn and natural sounds on the modern horn in the solo part. The piece requires four natural horns in the orchestra.

• A natural horn appears in the heraldry, or crest, of Gerardus Rubens.
• A natural horn is displayed in the Victoria and Albert Museum, London.