cornet mouthpiece - gr mouthpiece
A throat made with a drill No. 27 having straight sides for as much as 3/4 inch will tend to cause the player to play sharp in the high register. On the other hand, if the straight sides of the throat are too short, the player will tend to play flat in the high register. Thus intonational tendencies, either sharp or flat, can usually be corrected in the mouthpiece.
If the backbore flares out rather rapidly, the tone will be full but slightly more difficult to control. If the backbore becomes straighter, with less flaring out, the tone becomes thinn
own a common deficiency in which there is an appreciable gap between the end of the shank of the mouthpiece and the beginning of the mouthpipe. The two should meet. To correct the deficiency, the shank is turned down somewhat on a lathe so that it will be small enough to meet the end of the mouthpipe. A marked improvement in playing of the instrument is thereby effected.
cornet mouthpiece
gr mouthpiece
Figure L [to the left] shows a cut-away section of a mouthpiece and receiver pipe. Notice the substantial overlap from the end of the shank to the mouthpiece. This is a serious defect. Though it does not show a gap between the end of the shank and the beginning of the mouthpipe as in B, it is possible that if the shortcoming of B is remedied, the present overlap as shown in L remains.
The diameter of the inside of the mouthpipe at the point where it meets the mouthpiece shank is from .325 to .345 inches on most trumpets; however, since some shanks measure only .275 to .300 there is bound to be an overlap from the shank to the mouthpipe of 0.030 inches. This is the shortcoming shown at L.
In the correction of this shortcoming it is not desirable to ream out the shank with a reamer as this would change the contour too far up into the backbore. It is preferable to taper the shank opening with a cutting tool only about 3/8 inch. This the tapering remedies the shortcoming of L without appreciably altering the backbore of the mouthpiece.