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I have heard all about how "The Gap" can change the response of a horn. Here is a question - how does shank size change the intonation on a tuba? We are talking about moving the mouthpiece in or out a relatively small amount; minuscule in proportion to the length of the tuba. However, I have heard people say that so-and-so tuba only plays in tune when using a Euro (aka larger) shank, vs. the Stardard (aka America) shank of the exact same mouthpiece.

I am asking this, because I switched from a Standard to a Euro shank mouthpiece on the Schiller 186 wannabe. I much prefer the ergonomics with the mouthpiece sticking out a little more, and the receiver is large enough it can handle it. However, the last couple days the intonation tendencies have felt different to me. Putting it on a tuner just now confirmed it. The lower register wants to go a little sharp, and the high register a little flat. I can still play the horn in tune, but it feels different. Maybe it is me - the kids have been sick this week, so my practice time has been minimal and large ensemble rehearsals have been nil. Maybe it is because I switched from a #1 to a #2, with the #2 being more open. But, something just feels different with the pitch.

Really wish I could have kept the #1, as it was the perfect solo mouthpiece for the Schiller, but just a little too strident and punchy for all around use, and finances would not permit a second mouthpiece.

Would love to hear from people who played both a Standard / American shank back-to-back with a Euro / Large shank, and hear what they have to say about differences in intonation (not overall pitch.)

I have never noticed any difference in intonation between shank sizes other than occasionally the overall pitch.

When you insert a larger or smaller shank.... the 'gap' is what you are fooling with... aside from the obvious difference in the mouthpiece itself. I've always held that a 'gap' generates an air disturbance and less is better. I might be all wet on this but that's my opinion.

Unless.... you are using some of the European tubas that have no receiver. In the case of those tubas... there is no gap since the shank is actually inserted directly into the leadpipe.

I have got both a PT-65 and a PT65s with slightly smaller shank. I have noticed no difference in intonation with one over the other, but perceive that my PT-15 responds just that little bit better with the smaller shank.

However, I know PT mouthpiece have been enhanced over the years (with Bob Tucci tweaking to improve), so it could just as easily be that, as the smaller shank mouthpiece is the newer.

I am paraphrasing Matt Walters here, back in the days when Dillon sold and Adjustable Gap Receiver: In general, the further in the mouthpiece goes thus diminishing the gap, the more open the low register is, the fuzzier articulation is, and the upper register slots become less distinct. The further out the mouthpiece is thereby increasing the gap, the cleaner articulation is, the more slotted the high register becomes and the stuffier and less responsive the low register becomes.

My personal experience with a number of horns fitted with the AGR bears this out. At least in my experience. YMMV.

Chris Olka
Seattle Symphony
Seattle Opera

Doesn't this sound more like it's the change in Backbore (more open) rather than the change in shank size/gap that would be causing the intonation differences? I am by no means a mouthpiece expert, but from the reading and experimentation I've done, my understanding is that the backbore will cause the octaves to compress if it's too big. I think the AGR would be the only way to really experiment to isolate the cause and effects due to the gap alone. How about some authoritative comments from the real experts on this site? I'd like to know also. . .

Changing the distance a shank goes in does, in effect, change the backbore. The results of that change are not always predictable. Once you assemble mouthpiece to instrument, it becomes one resonance and the individual charateristics of each no longer totally apply... in my opinion. You just have to try it and see what happens.

Doug "who knows that some people don't agree with this" Elliott