Unlike the other components, the backbore is not generally measured in specific sizes as they do vary in terms of shape and taper. Manufacturers design a backbore that works best with whatever combination of rim, cup and throat are present on the mouthpiece in question. As with the other parts though it can have a significant effect on the tone, pitch and volume of the instrument.

More conical backbores give a richer tone, while more cylindrical ones give a brighter, more projected tone. tpt Fairly cylindrical

The backbore is the chamber that transfers your breath to the horn and its shape and size can produce a brighter or darker tone, raise or lower volume/projection, and raise or lower pitch. A well designed backbore helps maintain good intonation throughout the instrument’s range.

The backbore that has emerged as the best in all-around performance, tone, and popularity is one that’s neither very large nor small, with a smooth, slightly curved taper from the throat to a well-rounded, even backbore.

While important to sound, feel, and performance, the throat and backbore are matched to the cup and rim by the mouthpiece manufacturer and are of less concern. When all’s said and done, most players will find that a mouthpiece with a medium cup and rim will suit them quite well.

Armed with this information, along with the feedback from your mouth during play, you’re ready to begin your search for the ideal mouthpiece.