The effects of the mouthpiece and bell on the frequencies of the vibrating air column in a trombone can be demonstrated quite readily by first calculating the expected resonant frequencies of a piece of PVC pipe that is the same length as a trombone, then replacing portions of the PVC pipe of the same length with first a cup-shaped mouthpiece and then a flaring-bell section of a trombone. The trombone components used were from a new pBone plastic trombone that is not only much less expensive than a regular instrument, which is made mostly of brass, but also features components that are much lighter than those of a conventional brass trombone and is therefore easier to work with.