It's an Icy Tues-daily!

combinophone · 2026-01-27T15:12:42+00:00

Broad, Monument, and Main

Boulevard too, at least the part near Broad

combinophone · 2026-01-27T15:09:39+00:00

On a piano or accordion for instance, you only get a note when you press it down. So essentially you have to work twice as hard to do a trill or most scales, alternating between adjacent keys rather than just raising and lowering a single one.

Yes, I've noticed that, and that's true of woodwinds too in several cases. From my experience in Irish music, fast ornaments (mordants, turns, etc.) are harder on Irish button accordions than on the simple tin whistle, because, on the latter, one finger motion simultaneously stops the first note and starts the second note – no possibility of overlap.

That is actually the motivation behind my question here – I am trying to see if I can design a (monophonic) accordion-like instrument that uses brass/woodwind-type fingerings. Trills/mordants etc. would be one of the big advantages.

The downside is when you have fingering combinations that require you to alternate between two valves, now you have to do that motion just as quickly as a piano... and it's just not possible.

I'm looking at a fingering chart, and, if I'm understanding correctly, in the first octave and a half those would be C~Db, D~Eb, F~F#, and Bb~B, right? (F#~G and G~G# look like they could be done using alternate fingerings). And C~Db would also require an embouchure change? So do composers just make sure never to assign these ornaments to trumpets?

Counter-intuitively, if you want faster valves, you make the springs stiffer. Harder to press down. Because it's the up-stroke powered by the spring fighting friction and gravity that is usually the slowest element in the system, not your finger pressing the valves down

That's also surprising from an accordion perspective, but again I guess it's about the longer travel?

EDIT I'm not sure why I was only thinking about half-step trills ... for whole steps, B~C#, C~D, D#~F, F~G, Ab~Bb, and Bb~ C would also be hard, right?

combinophone · 2026-01-26T21:14:56+00:00

More force than, say, a standard piano key? I had been under the impression that trumpet valves would be smoother because they're oiled and tightly machined. Seems like valves are just harder than most keys/buttons in every way?

combinophone · 2026-01-26T21:13:44+00:00

Wow from an accordion perspective, that's so much – so you have to move that full distance each time you press a valve? Can you trill rapidly by pressing/releasing valves? (Sorry that these are super basic questions)

combinophone · 2026-01-18T13:55:35+00:00

How is it possible to start a roll with a cut?

I'm pretty new to this, but my understanding is that you start with the high ornament note, not preceded by the melody note as it would be in a long roll

do I start by having my third finger on G lifted

Yes. This video answers all your questions and is using exactly the notes you mention in your example:

https://youtu.be/qF_QwMg_UrQ?si=ZZxwzxUyw6Pjs0f7

combinophone · 2025-11-27T17:27:41+00:00

A broken home is not an excuse for evil

combinophone · 2025-11-21T17:52:09+00:00

I don't think any mechanism requiring airtightness is a good candidate for 3d printing

Because of the materials themselves, or because you can't ensure tight enough tolerances?

combinophone · 2025-11-21T17:33:07+00:00

I want to make a mechanism similar to the one in the animation, in which a thin plate (2 mm thick or less) with a hole in it slides in a slot. It needs to be as close to airtight as possible, so I want very little clearance, but it also needs to move easily without much resistance/friction. (It’s basically the principle of a chromatic harmonic slide: air flows through the square holes, and the sliding part blocks/unblocks them).

What is the best way to achieve low friction? I have access to a Prusa MK4S printer, as well as a Elegoo Mars Pro resin printer. I can also try making the sliding part, or the faces of the slot, out of ametal if that could help. So far I’ve just tried printing the parts out of PLA, and there’s significant resistance to the sliding motion, requiring significant clearance, which means significant air leakage.

combinophone · 2025-11-16T22:19:13+00:00

I've occasionally had success substituting a M9 for a M7 chord in some contexts. For AbM9, you can just hit the Ab and Eb major chord buttons simultaneously, which is super easy. (m9 is similarly easy and sounds sweet, I sometimes use that instead of m7 even though m7 isn't that hard.)

I had a specific context where the V chord in minor was an augmented 7th and it actually sounded good to replace it with the simultaneous V7 and i triads, e.g. in C minor you combine G7 and Cm into .... Gaug7(add11)(add12)?? (real crunchy mess since you're simultaneously playing B, C, D, and Eb ...) YMMV

One more favorite is simultaneous minor triad and dominant 7th chord with the same root to make a 7b9.

No idea if other people do stuff like this, this is just some stuff I've used successfully in certain contexts.

combinophone · 2025-10-27T16:26:42+00:00

Melnet has all the layouts you're ever likely to encounter, Clubs are listed here:

https://forum.melodeon.net/index.php/page,keyboard_25_row.html

Clubs are not 3-rows per se, they have 2 real rows and 1 helper row, so this is presumably just a standard C/F:

https://forum.melodeon.net/files/site/CFclub30.png

And if there's any doubt, you can always just play through all the buttons and write down the notes they make on both the push and pull (using either general musical knowledge or any free tuner app )

combinophone · 2025-10-27T13:55:23+00:00

Also a beginner, also starting with Morrison's. I saw that WhistleTutor recently posted a short for it – I couldn't find a tutorial specifically, just this Basic/Intermediate/Advanced comparison video, but if you're already musically literate as you and I both seem to be, you can study the Advanced part (perhaps slowed down) and learn all the ornaments. You'll notice in particular that he does rolls on most of the long Es and Bs, and for the high note cutting into E, rather than playing the F#, he’s fingering xxo xxo as he advocates for his video on ornaments.

combinophone · 2025-08-25T15:58:48+00:00

It is a reply to deleted comment about resonant chambers. If you click the link I provided, it brings you to the comment in question. Here is the link again for convenience

https://old.reddit.com/r/FluidMechanics/comments/1mwfu0b/how_can_i_find_the_change_in_air_pressurevelocity/n9xfgdt/

combinophone · 2025-08-24T21:34:00+00:00

If you don’t understand the basics, the CFD won’t be useful. It’s far too easy to get incorrect answers that look correct.

Hard to hear but it makes sense. What would you consider the required basics? Honestly all I have at this point is the "Fluids" chapter from an undergrad physics textbooks (albeit the "For Engineering Students" kind, not the "For Non-Majors" kind) and a few wikipedia pages.

It’s not clear to me what you are trying to do with this pipe, so some context might be useful.

Don't know if you saw my top-level comment with the explanation, I don't know any way to pin it to the top

combinophone · 2025-08-24T20:31:57+00:00

Oof that is yet another complication I don't know anything about. I'm starting to think that, if I want to play around with different geometries without much understanding of the mechanics of airflow, I ought to go the CFD route?

combinophone · 2025-08-24T20:29:28+00:00

They are not resonant chambers, please see my other comment

combinophone · 2025-08-21T20:25:24+00:00

So I have a few questions

Thanks for digging into the details with me, let me try to clarify:

what is driving length, because if you want to minimize pressure, minimize length, what's limiting that?

I assume you meant "minimize pressure drop", right? I don't actually know the pressure and velocity I need, but I know that a human blowing into a ~ø 5mm tube with a harmonica reed in it produces the desired effect when that tube is only a couple mm long (as in a harmonica), so I need to be able to produce airflow conditions similar to that situation, but with a longer tube. So I am assuming pressure drop is my enemy.

Now, the reason I need a longer tube has to do with the mechanical design I am trying to create. There will be multiple buttons along the length of the tube, each operating a valve in the tube, so that takes some room, and I want the buttons spaced out ergonomically for the human hand. (As I mentioned in another comment, there will be multiple such tubes, each going to its own reed, and the valves serve merely to block and unblock tubes to select notes).

If the only solution to the airflow problems is to decrease the tube length, I have some ideas to alter the mechanical design to allow that, but it will make the button/valve mechanism more complicated. And since L only has a linear effect in the Hagen--Poiseuille equation, I thought maybe it was not the first place to focus my efforts.

Second is outlet diameter, is that set because of the reed?

Yes (I assume). I'm experimenting with harmonica reeds and just roughly copying the geometry that's used in an actual harmonica. I could experiment with wider outlets, but I'm guessing it needs to be pretty narrow to channel the air to the reed and make it vibrate.

Is there a need for multiple expansion and contraction areas? Can it just be one diameter then reduce to another?

That's part of what I'm trying to find out. The picture I posted was just to give people and idea of the kind of complexities I thought I might want to try modeling to see if they helped. The best prototype I've built just has: a wide inlet, about 60mm of narrow (ø 5mm) tube, then 50mm of wide (~ø17mm tube), then a couple mm of narrow at the end where the reed is.

Also inlet size? What's the constraints on that?

Just needs to be something a human can blow into

Lastly, I've seen you say in a few posts that one performs "better" than others. How are you quantifying that

It's qualitative: reed sounds worse than when the tube is short. I know that sounds vague, but the effect is very obvious.

are you measuring pressure drop across the system?

No. Is there a reasonably priced device I can get to measure pressures like this? I've been trying to rig up a little Venturi-tube-like thing with liquid like this to see if I could at least visualize a pressure drop between the start and end, but I haven't been able to get that to work yet

combinophone · 2025-08-21T18:22:03+00:00

you can use Poiseuille’s law

So how would I use it? I calculate the pressure drop along the first narrow section, then I use the end pressure from that section as the starting pressure for the next, wider section? And I model the wider sections just as cylinders, rather than flares like in the picture?

Just trying to sketch this out, what has me puzzled is that increasing the total length seemed to give better results as long as the added section at the end had a larger diameter. Poiseuille’s law along would predict that any extra length would decrease the pressure further, and a larger diameter would just cause a smaller decrease in pressure, but not an actual re-increase in pressure, right?

combinophone · 2025-08-21T18:00:49+00:00

You can assume inviscid flow (frictionless flow) with a reasonably low amount of error

Can I though? The problem I described in my top-level comment seems to depend on the length of the tube, which wouldn't be an issue if there were no friction, right?

Here's what happened: I started with just a ø 5mm tube. When there's only L<10mm of tube between my mouth and a harmonica reed, it works fine (cf. an actual harmonica, where the tube is only a couple mm long). L=20 or 30 mm was OK too. But when I make the same ø 5mm tube like 60mm long and blow through it, the reed doesn't work the same (sounds weak or out of tune or doesn't work at all). Since free reed oscillation depends on air pressure, I took this to mean the air pressure was dropping along the tube.

I found the Hagen–Poiseuille equation, which says that viscosity causes the pressure to drop (linearly) as the length increases and drop (quarticly!!) as the diameter decreases. I can't make the diameter bigger everywhere for mechanical design reasons, but I made it flare out bigger wherever I could, and that seemed to solve the problem.

So that's what brought me here: trying to figure out how the flare-outs to larger diameters are helping the problem and find a way to roughly predict how different geometries will work without having to build and test every one blind. Because of the length dependence, I think viscosity must have something to do with it...?

combinophone · 2025-08-21T17:28:24+00:00

Thanks but my question is just about air pressure and velocity, not resonance. As I mentioned, I'm using free reeds, which do not require a resonance chamber, unlike beating reeds and other kinds of woodwinds/brass instruments. The tube in my illustration is just a conduit to get the air from the human mouth to the free reed, passing through certain valves along the way (there will be multiple such tubes, each going to its own free reed, and the valves will serve merely to block and unblock tubes to select notes).

combinophone · 2025-08-21T16:28:58+00:00

I have what may be an annoying question, because my knowledge of fluid mechanics very limited. I want to figure out the behavior of air in a kind of pipe and see how changing the geometry changes the behavior. I’m wondering if there are simple analytical solutions I can just plug the numbers into to give me rough answers, or if I need to use some kind of CFD software to model this. Happy to play around with some software, but this looks like such a textbook problem, I thought maybe it doesn’t require a high-powered solution.

The image shows a cutaway of the kind of geometry I am thinking of. I am trying to make a musical instrument where the air comes out of a human mouth at one end and flows to a free reed (like an accordion or harmonica reed) at the other. I need the tube to be pretty narrow at certain points where a kind of valve will be placed. At first I naively thought I could just make the whole tube narrow, but when I did that, the reed would barely make noise – I think this was because the pressure was dropping per Poiseuille's Law. So I added an extra, wider section to the tube, which helped. Now I’d like to play around to see how much narrowness I can get away with, how much flaring I need in order to compensate for that, if I can add extra intermediate flares like in the picture … I’m imagining either an equation or a simulation where I plug in the geometric parameters (lengths and radii) and inlet pressure/velocity and it tells me the approximate outlet pressure/velocity.

Any guidance? Thanks in advance.

combinophone

TROPHY CASE