In my recent post, I discussed the bore of an instrument. In brass instruments, the bore of an instrument can be described simply as the diameter of the piping. For example, the trumpet is cylindrical bore instrument. The fact that the diameter of the tubing neither increases nor decreases until it reaches the bell gives the instrument what is perceived by the human ear as a harsher and brighter sound.
A conical instrument’s tubing gradually increases in diameter up to the bell. This creates what is perceived by the human ear as a mellower sound and can be found in cornets, flugelhorns, and other instruments not related to the trumpet.