- Earliest forms: Earliest forms were natural brass instruments, with no valves or keys.
- Invention of valves: In the early 19th century, valves were invented, which allowed for a wider range of notes.
- Addition of keys: Keys were added to improve intonation and facilitate certain passages.
- Double horn: In the mid-19th century, the double horn was developed, which allowed players to switch between two different crooks, changing the pitch of the instrument.
- Triple horn: In the late 19th century, the triple horn was invented, adding a third crook for even greater versatility.
- Modern French horn: The modern French horn typically has four valves, three crooks, and a range of over three octaves.
These changes have greatly expanded the technical possibilities of the French horn and allowed it to become a versatile and expressive instrument in classical music and beyond.