The stem or shank of a mouthpiece is the section, part of which, sits within the receiver of the instrument, that’s the section at the end of the instrument which is tapered so as to accept the mouthpiece. On this site, we have adopted the terminology of stem for this part of the mouthpiece, on the advice of Arnold Myers. You will also find it referred to as the shank in other publications.

Each mouthpiece is provided with three different stems which are selected with the stem size slider. In some cases, the different stems will be for different instruments, such as on the trumpets where stems are provided for the trumpet (the default setting), the flugel horn and the cornet. On the trombones, the different settings provide for the different shank sizes found on mouthpieces for these instruments

It is important that the mouthpiece sits snuggly in the receiver, does not wobble and is seated to the right depth. Generally, if you have a newish instrument and a modern mouthpiece, there should be no problem however, there may be some occasions when you wish to adjust the relationship between your mouthpiece and instrument and this is where the PeakTone mouthpiece site comes to the fore. The diagram below shows the nomenclature used on this site to describe the stem elements which are editable, these being, Stem Receiver Diameter, Stem Receiver Depth and Stem Lower Diameter.

Unfortunately, not all receivers are created the same as some have a step at the instrument end, here referred to as the receiver lip, while others pass smoothly into the instrument’s windway. On those which have a step, it is important that the gap between the mouthpiece and the end of the receiver is as small as possible.

The diagram below shows a mouthpiece fitted into a receiver with a stepped windway:

It is important that the gap between the mouthpiece and the receiver step is as small as possible and the diagram below shows a mouthpiece inserted into a receiver which generates an excessive gap:

On receivers which lack a step, the question of gap size does not arise. The top diagram on this page shows such a mouthpiece/instrument combination:

In general, trumpet mouthpieces have stepped receivers while flugel horn receivers are stepless. Most cornets are like trumpets in this regard but a few makes feature stepless receivers.

A key feature of a mouthpiece/instrument combination is the length of the stem which seats inside the receiver. On this web site, we refer to this as the Stem Receiver Depth. As one might expect, a mouthpiece/instrument combination with a longer section of the mouthpiece exposed, (a low Stem Receiver Depth) will be flatter than one in which the mouthpiece seats further into the receiver as it it, in effect, lengthening the instrument.

The features on the PeakTone mouthpiece site are designed to enable you to overcome the following mouthpiece/instrument problems:

Measuring the Parameters

Stem Receiver Diameter

This is the diameter of the stem at the point where it enters the instrument’s receiver. Technically, therefore, it is not a mouthpiece measurement but applies only to a particular mouthpiece/instrument combination. Nevertheless, in practice, it is a measurement of great importance in many ways. For one, it is a dimension of the mouthpiece which is used to calculate the slope of the stem taper, and hence, how well it fits in the instrument receiver. For another, in collaboration with either the stem receiver depth and/or the stem lower diameter, it can be used to decide how deeply the mouthpiece fits in the receiver, affecting either the mouthpiece/instrument gap or the tuning of the mouthpiece/instrument combination.

It is best calculated by means of a digital caliper, as shown on the illustration below. If you are not familiar with this measuring device, please check the page: How to Obtain and use a Digital Caliper.

Stem receiver Depth

The illustration below shows the dimension referred to on this site as the Shank/Receiver Depth. This is the measurement from the end face of the receiver to the surface of the lip at the bottom of the receiver.

This dimension is one of the three used to calculate the taper of the shank or stem, the other two being the Shank/Stem Lower Diameter (that at the exit end if the mouthpiece) and the Shank-Stem/receiver diameter (the diameter of the Shank/Stem at the point where it enters the receiver or the diameter of the receiver entry point). This diameter is most-commonly adjusted when fitting a mouthpiece shank taper to a receiver. This process is discussed here.

It is best calculated by means of a digital caliper, as shown on the illustration below. If you are not familiar with this measuring device, please check the page: How to Obtain and use a Digital Caliper.

Stem Lower Diameter

Fixing a Poorly Seated Mouthpiece

There are two basic ways in which a mouthpiece/receiver combination can fail to prove adequate, one being where the mouthpiece stem taper is steeper than that in the receiver and the second where the mouthpiece stem taper is less than that of the receiver. In the first case, the mouthpiece will rock against the edge of the receiver while, in the second, it will rock against the bottom end of the receiver.

When poorly seated, a mouthpiece will wobble and may, under some circumstances leak, causing problems with both tone and intonation.

In the case where the mouthpiece taper is too steep, it may be adjusted by increasing the Stem Lower Diameter, in which case,  mouthpiece/receiver combination will remain at the same length. It may also be fixed by reducing the Stem Receiver Diameter, in which case, the mouthpiece will sit more deeply into the receiver. Care must be taken when doing this to ensure that the mouthpiece does not bottom on the receiver lip when such is present.

Stems are generally a standard size for trumpets, cornets and horns but for trombones and lower brass there are Small and Large Shank options. Generally, student and small bore instruments use the small and professional and larger bore instruments use the large. There used to be a medium sized found on older Boosey & Hawkes instruments (pre 1974) such as the imperial euphonium and it is still possible to purchase a mouthpiece with this shank if required.

method for overcoming such problems are discussed on the page Fix a Badly-Fitting Mouthpiece