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. Carl may have swapped out more mouthpipe tubes over the years than have I, but I have possibly observed (hypothesis, and not any sort conclusion) that smaller mouthpipe tube choke points (more simply put: mouthpipes that taper down to a smaller inner diameter, compared to others) tend to raise the overall pitch level of a brass (wind?) instrument (at least, a tuba) compared to mouthpipes with larger choke points.

I have an idea as to why, but if there is already a conclusive reason as to why, I'd be curious to see if it lines up with my hypothesis. (yes: the same mouthpiece, the same temperature, the same main slide position, the same complete warming-up, etc.)

Even when I lengthen an instrument (sort of significantly) and reduce the choke point (let's say, by 30/1000ths or perhaps even a bit more) the overall pitch level tends to be higher (yes, with a tuning slide and room temperature in the same position, after warming up an instrument completely).

I suppose I could show a picture of one that I recently did, but it's probably not going to be very interesting. What's more interesting to me would be your knowledge and response to the question.

(This has nothing to do with the physics and the science of the question, but a few of you may have picked up over the years that I prefer smaller choke points, as well as shorter/closer setbacks of mouthpieces (not very much exposed reverse taper from the receiver) from choke points. With bass tubas and related instruments, I seem to be perfectly happy with a choke point around or only a little bit larger than a half inch, and - with contrabass tubas of various sizes - I sort of seem to like about .520" or maybe .525".... but this last add-on paragraph is neither here nor there and is only a sidebar expressing my personal preferences regarding built-in mouthpipe resistance... Yet resistance and the venturi dimensions may be the key to the entire question. ??)

Ok doing the typical professor thing and wildly overstepping my specific area of knowledge.. but I've been reading Arthur Benade's work on brass instruments. He wrote a lot of stuff that isn't on his textbook "Fundamentals of Musical Acoustics"

He stressed frequently the leadpipe and mouthpiece region are not merely "part of the tubing length." They are impedance transformers and are important for determining:

peak height

peak width

peak spacing

input impedance phase

Changing the transformer can shift resonances and alter the "effective" acoustic length more than changing a surprising amount of cylindrical tubing elsewhere.

In your example a change from 0.550" venturi of 0.030" that's a 12% reduction in cross sectional area. The proportional change of a few inches on 18 or 16 feet is much less.

Benade modeled the mouthpiece to leadpipe as an asymmetric converging (cup to throat), diverging (backbore), converging (venturi), diverging( leadpipe) system.. Really complicated stuff when you get into all the differential equations with boundary conditions. The cool thing is he was often validating with real science the stuff that guys like you figured out from experience.

Thank-you.

Believing that I strive to be sensitive enough and observant enough to not imagine things, and always attempting to be a skeptic (of myself, just as much as I am of others) - demanding to be thoroughly convinced of something rather than just being told something by a person or a book or a consensus - even though you didn't go into deep specifics (which probably would have been over my head) I really appreciate the response.

To go beyond the scientific research (whereby you have explained to me that I'm probably observing things as they are) and to step away from that and to go on to defend personal preferences, I believe that I've determined that - down to a certain diameter range - I'm not restricted by how much sound I can produce nor the quality of the sound I can produce (actually/seemingly a superior quality of sound) when approaching this diameter "sweet spot". Additionally, overtone tendencies seem to be closer to where they would appear on a chart of mathematically predicted overtones, rather than being being as wild as they are on some makes and models of instruments (whereby one's eyebrows tend to jump up fairly high in response to what some of those wilder instruments apparently prefer to do). Even with a terribly out of tune tuba (which continues to be terribly out of tune) such a choke point just passed the mouthpiece might help the tuba be not quite as terrible or - if remaining just as terrible - possibly easier to favor.

That said, (as pretty much everyone already has discovered) there's no "magic bullet" and everything seems to affect everything.

example of a specific model which was horrendous, shelved, redesigned quite a bit later, and then released again onto the market with many changes:
That said, that absurd intonation tendencies circa 1990 or so rotary instrument released by Meinl-Weston (2155 - huge mouthpipe, huge bore size, huge sound, horrible open tuning tendencies) - which was taken off the market and put back on the market decades later as a piston tuba designated as 5450 - features (now) a much smaller mouthpipe tube (basically borrowed from one of the same manufacturer's F tuba models, whereby the choke point is somewhere in the .520" range, and the large end of the mouthpipe doesn't even make it up to the size of the 19mm valveset bore). Of course, the 5450 features some intonation flaws (what tuba doesn't?), but it's far less work to play with at least as much sound output, and the intonation flaws are minor, vs. the rotary 2155 sporting ridiculous and nearly impossible to overcome (non-western music aligned) intonation tendencies.

something else with a choke point in my preferred diameter range, which seems to be quite easy to favor (hopefully not many) pitches whereby there's no convenient mechanical solution to dial in the length of the air column:
I just altered a 4/4 contrabass tuba of mine and dialed the choke point down into that range (I posted about this and drew some pictures) from considerably larger, and it's much more of a pleasure to play and much easier to favor the few pitches that need to be favored. Another thing (about what I was very skeptical, and not trusting myself and my own observations for several days) is that the fourth partial ("tuning note") not just crept, but "jumped" up to In tune from being flat.

The formidable Fat Bastard (Miraphone 98) :
features a conservative choke point just past the mouthpiece, whereby there are a couple of pitches which I can only mechanically favor most of the way, or which are too inconvenient to mechanically favor. (ex: I simply refuse to play second space C-sharp with second and third valves, and I'm only willing to play it with second valve alone.) That particular pitch is so very flexible with this instrument that I can VERY easily play it in tune or even sharp (though centers flat) without having to change anything detectable either regarding lip tension, air, or quality of resonance, and only having to pay attention to the tuning with my ears.
This isn't a brag on "bloke's great instrument", but I'm tending to attribute this ease of favoring of pitches with this huge instrument to the conservative choke point in the mouthpipe tube.

Typically, this was too long so if you read it, you deserved it.

I've been sorta thinking about this for a while, including the human factor. I'm of the opinion that some people may experience intonation tendencies different than others for the same horn because of physiology.

For example, bloke has talked about the Yamaha 411 sousa being sharp on low BBb, and the same for Holton 345/350 BBb tubas. I do not have that tendency on those horns -- low BBb is fine for me. Open F below the staff actually blows a little sharp for me on the YSH-411.
Also, I mentioned (as did arpthark) that those sousas blow sharp for me -- even with the tuning bits -- so I have to pull the MTS out quite a bit to get down to A 440. But bloke did not experience those blowing overall sharp for him.

I have one of those so-called 'horrendous' horns, and the intonation tendencies are there. But not as severe as other's experiences with that model. Bottom line G/Gb wants to play about 15c flat relative to other open notes for me. NOT 30+c flat like some have mentioned. And no super saggy 5th partial, and no sharp 6th partial. They are all pretty close. The sound and response are fantastic, as is the build.
I did install a smaller mouthpipe on it many years ago, and it does seem to make the response easier, and intonation tendencies easier to deal with. But they are still there.
Maybe mine is a better example of that model
But I also suspect that my personal physiological (embouchure/oral cavity) intonation tendencies may 'line up' better than some, and vice versa on particular horns.
There are other horns I've played that had more severe tendencies

I'm thinking that is in part why some can 'deal with' troublesome horns better than others, and why we sometimes have different experiences regarding horns and mouthpieces.

It's pretty easy to sag a sharp second partial (B flat or C below the staff) with the lip muscles when playing a contrabass tuba - but only until we add so much cylindrical tubing that we can't overcome the tendency anymore (G flat or A flat played on contrabass tubas - valves 2 & 3).

By the same token, the same pitches an octave higher (around the bottom of the staff - also 2 & 3) tend to be saggy on many brass instruments. I'm pretty sure that what's happening is that - after we add all that tremendous percentage length of cylindrical tubing, we've really messed up the conical taper, whereby everything is really out of kilter.

Even though trombones are much less conical and much more cylindrical, trombonists joke about the equivalent of valves 2 & 3 (5th position) because it's so far out on the slide and the three different pitches that they play there are all in very noticeably different specific places. (Something about Pooh asking Piglet about where the fifth position is on the trombone, and Piglet answering back to Pooh that no one knows)

4th valve distorts the intonation of the overtone series even more, but we don't use it above C or D on a contrabass tuba, so we don't complain about it very much, if at all.

Not to demean your observations (which are quite valid), but those are naturally occurring and predictably occurring things (completely expected and fairly consistent) whereby long sections of cylindrical tubing mess up the overtone series, rather than (what I was sort of intending to be the topic) the expanding bugle itself (whether a large diameter section of it or a very small diameter section of it) messing up an ideal (not in equal temperament, but in physics, numerically) overtone series.

...but (demonstrating respect for your related topic) it's probably actually the same topic because - whether there's any absolutely cylindrical tubing or not interrupting the taper of a brass instrument bore - my topic still is overall bore tapers which are not ideal (whether for intonation, response, or tuning flexibility).

As we've read about, modern day computer models can offer "best overall compromises" for most any given overall size and length of brass instrument, and my primary observation is (it just seems to me) that now that such computer programs are utilized, a whole bunch of the more recently developed models of tubas feature smaller choke points just past the mouthpiece.

noticed: (related to computer optimization of bore tapers)
I personally have not encountered any of the newest models (even 6/4 contrabass) which feature epically saggy third partial tuning (open F or G) compared to this being so much more common with legacy models (whereby the only viable solution was to resort to playing those pitches with valves 1 & 3... and (this difficult issue) even as recently as Chinese models designed only a decade ago or so and certainly German models designed around the 1990s featuring this stumbling block,).

My old Holton BBb always had the main slide out about an inch or so... until I got a nice ding in the main bugle right after it exits the valve block.. Now it's noticeably flat.. and I have the slide all the way in even on hot don't days. The worn valves don't help either. I've day i'll find s cheap valveset and fix it... but until then I just live with it.

gocsick wrote: Thu Jun 11, 2026 8:48 pm My old Holton BBb always had the main slide out about an inch or so... until I got a nice ding in the main bugle right after it exits the valve block.. Now it's noticeably flat.. and I have the slide all the way in even on hot don't days. The worn valves don't help either. I've day i'll find s cheap valveset and fix it... but until then I just live with it.

There was a member on the old forum who primarily played, iirc, a B&S F tuba and also had a Bb Weril for I can't remember what (quintet gigs?). His F tuba got dented somewhere and it 'fixed' a lot of response issues to the extent he told the techs he took it into to get cleaned to not fix it. He had an interesting comment that, iirc, low F was better on the Bb and low Bb was better on the F.

iirc, he was dealing with focal distonia issues and ended up listing his tubas shortly before that forum went haywire. Steve something maybe? Not Steve Eb/56j from Indiana, I think he also played double bass and bass guitar.

Bob Kolada wrote: Fri Jun 12, 2026 1:17 am

gocsick wrote: Thu Jun 11, 2026 8:48 pm My old Holton BBb always had the main slide out about an inch or so... until I got a nice ding in the main bugle right after it exits the valve block.. Now it's noticeably flat.. and I have the slide all the way in even on hot don't days. The worn valves don't help either. I've day i'll find s cheap valveset and fix it... but until then I just live with it.

There was a member on the old forum who primarily played, iirc, a B&S F tuba and also had a Bb Weril for I can't remember what (quintet gigs?). His F tuba got dented somewhere and it 'fixed' a lot of response issues to the extent he told the techs he took it into to get cleaned to not fix it. He had an interesting comment that, iirc, low F was better on the Bb and low Bb was better on the F.

iirc, he was dealing with focal distonia issues and ended up listing his tubas shortly before that forum went haywire. Steve something maybe? Not Steve Eb/56j from Indiana, I think he also played double bass and bass guitar.

You are thinking of Steve Hoog, who had the "magic dent" in his F tuba, but I don't recall and can't find any evidence that he suffers from dystonia. I may be just forgetting, of course.

Rick "he posted as 'eupher61' on Tubenet" Denney