When a mouthpiece is seating badly in the receiver, it will wobble and cause difficulty when playing and possibly leak. The first thing to ascertain before carrying out any further investigations is whether or not it is the condition of either the shank or the mouthpiece which is causing the problem. If the mouthpiece has been dropped and squashed at some stage then this needs to be dealt with. Similarly, if the receiver is showing signs of damage this too might call for expert attention.

If both mouthpiece and receiver are in good condition, the problem is likely to arise from a mismatch between the tapers of the mouthpiece and the trumpet’s receiver. Unfortunately, not all makers adhere to the same standards when making mouthpieces or receivers, thus giving rise to this problem. The initial tapers of PeakTone mouthpieces are specified on the relevant instrument pages but these may be adjusted to suit your individual needs.

Checking the Mouthpiece Shank/Receiver Seating

Some mouthpieces have a lip at the bottom of the receiver and this may be causing a problem if the upper diameter of the mouthpiece shank/stem is smaller than than that of the receiver exit. In this case,  the mouthpiece might be seating on the lip. this is, of course, not a problem when the receiver in question has no lip, as on flugel horn and some other receivers. The illustration below shows two conditions which might be caused by this situation.

The illustration above shows the situation where the shank/stem is seated on the receiver lip.

To check for such conditions, please see Checking Shank/Receiver Depth

Before a seating problem can be dealt with it is first necessary to determine what is causing the problem and it can be caused by one of three conditions.

Mouthpiece Seated on Top of Receiver Outer Diameter

The first one is if the taper of the mouthpiece is greater than that of the receiver and the mouthpiece is seating on the outer edge of the receiver. Under this condition, when the mouthpiece is rocked, the top stays fixed and the bottom of the shank/stem hits the receiver wall. The condition is illustrated in the diagram below:

Such a condition may be dealt with as shown on the page: Fixing a Top-Seating Mouthpiece