The Horn Mouthpiece and Receiver Relationship: A Guide


French horn mouthpieces can be a confusing topic. The player is confronted with an array of choices concerning cup, rim, bore, diameter, and shank. The mouthpiece's relationship with the horn adds yet another dimension of complexity, with certain types or mouthpieces often being cited as "better" for one horn design or another. Success when choosing a mouthpiece can often be attributed to luck or recommendation. Other times, great results are achieved through will in opposition to a seemingly illogical choice. While there are no right and wrong answers, data trends do exist. For instance, thicker lipped players often (but not always) use wider diameter mouthpieces. High horn players often (but not always) use shallower cups. Most (but not all) Alexander horn players use relatively small bore sizes. Understanding these trends, as noisy as they are, can help the player make informed decisions when selecting equipment to consider. As always, don't be surprised if your personal experience represents a datum that runs orthogonal to the mean.

One aspect of mouthpiece design that causes a fair amount of confusion is the shank; in particular, how the shank interfaces with the leadpipe's receiver. Many questions around this relationship exist. For instance:

  1. What is the difference between an American and European shank?
  2. Why do mouthpieces with the same shank on paper insert to different depths?
  3. Is there a "correct" and "incorrect" fit?
  4. Why do horns all seem to have different receiver sizes?
  5. How does the shank-fit effect the playability/sound of a horn?

I would like to attempt to demystify this aspect of horn mouthpieces, but first a caveat: I am not a mouthpiece maker, horn builder, or acoustician. The information below represents my observations as a professional hornist and knowledge from consulting various experts. I will not be citing sources as I don't intend this as a scientific document. I am always open to revision of this article. If you feel you have better/more information or have been misquoted, please send me an email and help me revise it for greater accuracy.

A note about subjectivity: In this article I may use terms like "plays better" or "sounds the best." These are entirely subjective measures and I use them only for convenience. One player's "better" might be another's "worse". Our distinct physiologies and psychologies mean that either the science is too complex for absolutes, or art itself does not lend itself to objectivity. Either way, the focus here is not philosophy but practical application.

A good preliminary step to understanding the shank/receiver relationship is to measure it. Each horn and mouthpiece combination will represent a slightly different fit. The horn player may find interest in these measurements, if only to compare them. You will need a few tools to begin, namely a set of small-hole gauges and a digital caliper. You can get both at the hardware store or on For the small hole gauges it's important to get the type with a ball at the end and not a flat disc. French horn leadpipes are not always perfectly round and the ball can help identify manufacturing flaws. Here are some product links that might help: Small Hole Gauge Set Digital Calipers

Now, to the process: First, take the third largest size of small hole gauge and expand it so it barely fits in the entrance to the leadpipe receiver. Then, gradually turn the end-screw so the ball becomes smaller, pushing it inside the receiver. At a certain point you will be able to feel where the receiver starts to expand again into positive taper. Right at that point is the venturi, the smallest point in the leadpipe receiver. note: The term venturi is technically a misnomer here but I will continue to use it as I have defined above. You can take your thumb and put it on the side of the small hole gauge and then mark where that point is on the outside of the leadpipe with a Sharpie marker. Go ahead and measure 3 or 4 times very carefully to make sure you're hitting the right spot.

There are three caliper measurements that might interest you:

  1. The diameter of the small hole gauge ball right at the venturi point
  2. The diameter of the small hole gauge ball at the very top (entrance) to the leadpipe
  3. The distance from the top of the leadpipe to the venturi

You can measure two of these dimensions (1 and 2) with the digital caliper by lightly clamping the ball of the small hole gauge with the caliper's jaws. It is surprisingly accurate! The third dimension (3) you can measure manually with the caliper jaws.

With those three dimensions you can easily calculate the rate of taper. For ease, here's a website to help with the formula:

Taper Degree Calculator

The result here will give you an idea of the type of reamer that was used to create the receiver. There are three or four types of reamer that are commonly used to make French Horn leadpipes:

Morse 0 taper is about 1.49 degrees. The old European taper was closer to 1 degree. Metric is somewhere between them. Here is a reference with some info on various machine tapers:

Taper Reference

It's important to remember that any of the above tapers can be reamed into the leadpipe at any given depth, so the rate of taper does not at all predict the size of the venturi or the distance down to it. There are horns that use Morse taper that require thicker mouthpiece shanks, and some that require thinner ones.

Here are some measurements I have collected over time. The first dimension is the venturi size, second is the depth, and third on some of them is the dimension at the opening of the leadpipe.

Something that should be immediately apparent from the above data is that there is no one "American" or "European" standard for receivers. Manufacturers are all over the place and manufacturing tolerances contribute to the confusion. Even from year to year or from horn to horn, dimensions can vary greatly. The same can be said for mouthpieces and mouthpiece makers.

With the measurements you have made you can start to make an informed decision about a proper mouthpiece fit for your horn. Here are some things I have learned in my own experiments:

The general trend I observe is that horns with a larger venturi play better with smaller mouthpiece bores. Aside from that, it's easy to surmise that the tip of the mouthpiece shank should go exactly to the venturi but not beyond it since the positive taper in the backbore of the mouthpiece should ideally open smoothly to a positive taper in the leadpipe.

If the mouthpiece sits farther out so the shank ends before the venturi, there is a positive taper in the backbore followed by a negative taper as the leadpipe reduces to the venturi, followed by another positive taper as the leadpipe opens up. It's easy to imagine this not being efficient in terms of air-flow. Conversely, if the mouthpiece goes beyond the venturi, one positive taper spills over abruptly into a larger one.

In practice, it is not that cut and dry. Most horns plays poorly when the mouthpiece inserts too far. Certain horns and mouthpieces seem to play best when the mouthpiece sits right at the venturi. Others play best with a millimeter or 2 gap before the venturi. Even so, some mouthpieces seem to work better on the same horn with a gap, while others play well without one. Any hard rule about the shank and venturi relationship does not seem to hold water in the end.

People have varying opinions on the matter:

Bob Osmun thinks the only measurable difference will be in the cubic volume of the overall system which is reduced or enlarged via insertion depth. He believes the shank/venturi relationship doesn't matter.

Engelbert Schmid, the great horn maker says there should be a few millimeters (2-5) of gap before the venturi to equalize the step created by the thickness of the mouthpiece shank.

My own general observation is that the further in the mouthpiece sits, the more open the high range, the less resistance overall, and the less compact a sound. The further out the mouthpiece sits, the more resistant and notchy the feel, and more compact the sound. You can see EITHER way as helping or hurting projection. Another way to think of it is this: further in = more lip compression required/allowed, further out = less lip compression required/allowed.

The overall length of the mouthpiece seems to further complicate things. The longer European mouthpieces seem to feel more similar to shorter American mouthpieces that have a few mm of gap (so that the distance OUTSIDE the horn is actually equal between the two.) The late mouthpiece maker Scott Laskey agreed with this, which is why his European shank mouthpieces are just a thicker version of his standard shank.

In the end, the best way to find your mouthpiece fit is through repeated experimentation noting both the feel and sound. The info above should set you on course and provide some clues that will point you towards your best solution.

Updated: 2020.06.04