There has been some discussion on TPIN about C trumpets and intonation.

GR: This is a very deep subject that I could talk on for days. Using physics there are 2 inherent reasons for intonation problems on the C trumpet not including player:

1. The bell!

This is the area the pressure or standing wave is reflected back to the lips. The shapes in the Bell are a huge factor. Most C trumpets have Bb bells that have been altered for the C trumpet.

2. The mouthpiece & leadpipe are the other problems.

Most leadpipes are designed for the Bb and just cut shorter. 3. The player is a huge problem because we are all different. If you have a perfect acoustically designed trumpet and mouthpiece for one person it would not perfect for the next player due to the amount of lip engaged into the mouthpiece.

Lets look at the Mouthpiece & Bell.

Take a straight tube and note the overtone series. Adding the mouthpiece will drop the top partials and adding the bell will bring the lower partials up. The Mouthpiece and Leadpipe work together. When dealing with linear tubing either cylindrical or conical the speed of sound remains constant and length will determine pitch. When you deal with non-linear shapes such as the mouthpiece, length doesn't determine pitch but the VOLUME does. Therefore, it is the volume of the internal shape of the mouthpiece that determines pitch, minus the lip engagement. Lip engagement is one of the major keys the we overlook. We are doing simulations working with lip engagement and it has a huge effect. Add .001" of lip engagement and you will raise the pitch at high C by 2 cents because you have reduced volume!

ADDING THE MOUTHPIECE

When the mouthpiece is added we calculate the volume. The equal volume of straight tube is removed. The lowest resonance frequency will be unchanged but the upper will come down.

ADDING THE BELL

This is done to move the lower modes up. By flaring the end to a larger diameter (shape is very important) the BELL raises the frequencies of the lower resonances, the lowest moves the most. Length must be adjusted.

With my design program I can make a mouthpiece any length and have it solve the sound wave equation. I use length to adjust other things. I usually don't make a mouthpiece less than 3.4". Shorting a mouthpiece can have many effects both good and bad, using physics these effects usually cancel each other out.

Someone suggested you could take your normal mouthpiece and shorten it to make a C trumpet mouthpiece with improved intonation.

This would change many things and mostly make things worse if you just cut the end off with a hack saw. You would also have to turn the shank diameter down to make the gap correct. It may help a poor mouthpiece play a little better but I wouldn't count on it. It would destroy a GR mouthpiece.

I don't put any value in this thinking. I have found that there is a mathematical difference between the requirements for the C trumpet vs. the Bb. I use an area of my program to adjust for this. I feel in most cases the mouthpiece that works on Bb will not be the best choice on C and visa versa. Different things will work for different players.