Horn Lore📯 #6 Physics Part 2 - Conical bore.
There are two types of brass instruments. Cylindrical bore, and Conical bore.
Cylindrical bore instruments, such as trumpets, trombones, and baritones, have tubing that stays the same diameter though the instrument until the bell flair. Because of the consistent tubing, the sound in these instruments are very focused and piercing. That is the typical “brassy” sound brass are famous for.
The horn, euphonium, tuba, and cornet, by contrast, are a conical bore. This means that the tubing of the instrument gradually gets larger throughout. This gradual expansion is less focused and piercing, and results in a darker, warmer sound.
The horn, of all instruments, has the most extreme conical bore. The lead pipe where the airflow starts is extremely small, measuring only about 0.3 inches across. This flairs to an unusually large bell. This is key to extremely unique sound of a horn, which is described is being very dark, rich, and warm.
Conical bore instruments tend to be a bit more challenging to hit notes cleanly as the sound is less focused and less “slotted”. This makes it easier to bend the pitch with your lips, and requires more precision in note placement.