From my experience what Tunborough has just said is correct. I’ve been using perturbations in my head joints for many years and the upper octaves have always been in tune as well as the lower and that’s with a cylindrical bore.
I agree. So what shall we call this device? “Cylindrical insert” does not quite cut it IMO, although technically it is “a cylindrical insert placed in the cylindrical bore of a flute or whistle below the flute embouchure hole or whistle window to help bringing upper and lower octaves into tune with each other”.
What to call it?
An octave tuner, of course. 
I just have to mention for those not familiar with Reyburn whistles is that they are always perfectly in tune.
Whatever magic he uses, it works!
That’s interesting because the Killarney I bought back in 2014 has perfect octaves but the Killarney I bought in 2018 has the quite flat 2nd octave you speak of.
Here’s my little thread about those two Killarneys
https://forums.chiffandfipple.com/t/killarney-2014-v-2018/99741/1
Thanks so much for providing a fix for flat 2nd octaves, which as you know is a fairly common problem, from old Generations to many modern whistles, including ones costing hundreds of dollars. I’ll try your fix! (I have piles of brass and alloy tubing around in every conceivable size.)
BTW my fantastic-playing Colin Goldie Low C also has a slightly flat 2nd octave and I’ll try your fix in that one too. I’ll first try the blob of something.
Sorry but that’s just not acceptable to me. I need every note to be in tune, for professional work.
I have a whole roll of Irish whistles which are not flat in the 2nd octave, but produce every note from the low bellnote up to the 6th in the 2nd octave in tune, using a relatively even breath. Yes of course you have to change your breath to switch octaves but there’s no “pushing extra hard” to get an inherently flat 2nd octave in tune. (I don’t buy whistles like that.)
I’ve addressed it before (talking Low D’s now by the top makers) how different makers have slightly different approaches to the octave tuning, all of which can be blown into tune by the player, but having different pros and cons.
Some makers have the 2nd octave a bit flat, and it has advantages, giving you room underneath the 2nd octave notes. I had a particular Low D (old Overton?) which had loads of room there, you could underblow the 2nd octave so much that the notes were whisper-soft and still didn’t fall to the low octave. Yes those notes were very flat! But you could do cool effects, swelling the notes up to full pitch and volume.
The disadvantage to having the 2nd octave flat is that it exacerbates the already-present volume differential between the octaves, because you’re “blowing out” the 2nd octave and underblowing the low octave to keep them in tune to each other.
Then you have the MK with the slightly sharp 2nd octave, which also has pros and cons.
I prefer the octaves right in the middle, where most good Low D makers have them, where you can play on an even breath and everything is in tune. All the Reyburn, Burke, Lofgren, Susato, etc Low D’s which I’ve played have been right there, and my current Goldie Low D is quite perfect in the tuning all up and down the gamut.
Intonator? Pitch patch? Bracker octave enhancer?
Just as an aside comment, Shakuhachi makers which go way back have used these constrictions in the bore to tune their bamboo instruments. And they do this by painting lacquer (many layers) at different places in the bore to bring their instruments into tune. These are perturbations in the bore to change the airflow (or air pressure) so that’s what I call them.
What Mr. G said. And I wil add
that they’re all out of tune kids.
Not one been made that isn’t.
Get over it and start playing.
Get over it and start playing.
I’ll resume playing the whistle I have that is more in-tune than the other ones I have 
I was not suggesting it was indeed a fajardo wedge but suggesting its very similar. Fajardo wedges are use to correct intonation and indeed does have an effect on tone unlike this perturbation mod. Apologies for the confusion. As for the taper, it was referencing the flue and not headjoint 
. A wider bore headjoint is another way to help bring intonation in line. I have never seen a stepped cylinder flue. With the right headjoint, a cylindrical whistle or flute doesn’t have to be flat in the second octave yes indeed!
What Hans has done is the opposite approach to a wider bore headjoint by interrupting the node instead of the antinode of the fundamental.
The mention about concentrating on getting the second octave best in tune instead of the first octave comes from a discussion I had about intonation tuning and my thoughts on ensuring the second octave is best in tune is a matter of Auditory psychoacoustics where the ear does not identify out of tune notes in lower frequency note than higher notes. Have a read up about Auditory Psychoacoustics, it’s a very interesting subject. There are soo many instruments that have poor intonation and I know for a fact that all too many makers concentrate on getting the first octave in tune instead, on instruments with poor intonation, this is not the way to go in my eyes (not all makers are the same). That is the least acceptable scenario since it does make you have to push far too much to get the second octave in tune on a poorly voiced instrument, it’s easier to blow the first octave in tune than the second on instruments with poor intonation in many cases.
I have a whole roll of Irish whistles which are not flat in the 2nd octave, but produce every note from the low bell note up to the 6th in the 2nd octave in tune, using a relatively even breath. Yes of course you have to change your breath to switch octaves but there’s no “pushing extra hard” to get an inherently flat 2nd octave in tune. (I don’t buy whistles like that.)
Yes, you have most probably purchased instruments that are better tuned in the second octave and a tapered windway helps here. Window width as well as L/B ratio plays an important role with regards to how an instrument performs in both octaves. That is how much room you have in both. Hans has said that he needs to push second octave higher notes extremely hard to play them in-tune on his Killarney and is correct in saying it is common to cylindrical bore whistles.
The disadvantage to having the 2nd octave flat is that it exacerbates the already-present volume differential between the octaves, because you’re “blowing out” the 2nd octave and underblowing the low octave to keep them in tune to each other.
That’s another reason why I suggested concentrating on getting the second octave in tune as opposed to the first octave.
And I will add that they’re all out of tune kids.
Not one been made that isn’t.
Get over it and start playing.
Aint that the truth! 
[Thread revival. - Mod]
Hello! I´m new here and first of all I want to thank every one of you for such an interesting conversation. I was a silent reader of this forum for a while and finaly decided to register to thank hans for the information about this “tuning insert”. I´m trying to make some low whistles out of pvc tubing (following famous Guido Gonzato´s tutorial) and I did a couple that don´t sound that bad for my taste. My problem was tuning - as I´m not an experienced whistle player the difference between two octaves was sometimes 30-35 cents. I tried to make some “tipple wedge” type inserts but was not satisfied as they changed sound a bit too much for my taste. https://ibb.co/rvCyBxP
In search for the solution I found this topic and tryed to recreate this cylindric insert out of pvc tubing. https://ibb.co/W6TDsJW
As for my ears the result was much better, although my variant needs further modifications because low notes started to sound weaker and now tend to flip an octave. None the less I want to thank hans again and everyone on this forum. It´s always a pleasure to be here.
https://ibb.co/7SNw9Fm
Upd: changed images
That is not the case with most of my whistles.
For example, on my Colin Goldie Low D I can play up the scale from Bottom D to high B and every note is “needle straight up”.
Ditto my old Killarney high D (not the newer one as I said).
And as I’ve said I’ve played a number of Reyburn whistles in various keys and they’ve all been spot on.
I think people who imagine that whistles are out of tune by necessity must not have
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bought the right whistles
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learned how to fix not-right whistles.
Now there is a caveat! When I say the whole scale of a whistle is in tune I’m always referring to the G Major scale, the scale with C natural. To me that’s the natural scale of the whistle (no pun intended).
For sure C# is an outlier, at least it is in my opinion. It lays outside of the whistle’s normal scale, to me, and I think that makers who ruin C natural and in some cases even ruin the vented Middle D in order to make C# in tune to equal temperament are misguided. If having an in-tune C# and a messed-up C natural are the ideal for you, we will have to disagree on the nature of an ideal whistle.
To comment on the question.
I stopped my experiments with inserts to manipulate the tuning of the 2nd octave as I think it influences the sound too much. So I now make the holes larger, which will also sharpen the 2nd octave. The length of windway and window will also have an influence. With some experimenting I am pretty happy with the tuning even without any inserts.
I tried the bore restriction technique described on my own line of whistles (coming this fall) and found that it really added some harshness to the bell note, and weakened it quite a bit, even with knife-edge margins on both sides. I used a bore’s length of tubing, but I’m going to try half a bore’s length and experiment with positioning. Mine don’t really have much of an octave disparity, but I was trying to see if I could make the high octave even sweeter, since a feature of these is a bold low octave and sweet high octave.
What thickness are you using for your insert? I would recommend 0.5 to 1 mm, no thicker; for length, try starting around 10% of the bore length and go up or down from there.
I wonder if the top of the insert is interfering with airflow under the sounding blade. Perhaps a semicircular insert, that doesn’t reduce the bore immediately downstream of where the window is.
Just the standard 0.014" thick brass tubing. I honestly didn’t notice much of an effect on the high octave with a full bore’s length, so 10% seems pretty low, but maybe positioning is more of a factor there.
The airblade cut idea is quite interesting. I’ll try that as well.
Update: I’m not in my friend’s shop so I can’t part off a shorter section of tubing, but I did try the same 0.5" insert in the D tube instead of the Eb, and it had a much lower effect on the sound and seemed to have a bit more obvious effect in the high octave. Really curious to slice some of these up now. Anyone know what’s up acoustically here? Is the insert at the node or whatever of some standing wave? Reading up on instrument physics but it’s slow going.
A full bore’s length isn’t what we want. It’s the expansion of the bore between the headjoint (with the insert) and the main body of the whistle that changes the balance. As for positioning, if I were trying a semicircular insert, I’d start with it right at the top, against the fipple.
14 thou, 0.36 mm, might be on the thin side, but you work with what you got.
Reading this again… when you say “full bore’s length” and 0.5", were you talking bore diameter? I meant 10% of the full length of the whistle.