complex bore of R&R flutes?

[paddler]

I've sent Tunborough a complete set of measurement and tuning data for an anonymous keyless Irish flute that I have which seems to play well.
I would categorize it as a large hole, large bore, Rudall-inspired design, but I do not know precisely what it was derived from. Anyhow, we'll get
back to the group if anything interesting develops there. By the way, Terry, just pm me if you are interested in the data I sent and I'll forward you
a copy.

I did want to mention another thought that occurred to me as I was collecting the data for Tunborough. When we extend the tuning slide a long
way on these antique flutes it creates a cavity in the cylindrical head section of the bore from where the inner part of the slide ends up, to the beginning
of the body of the flute. That cavity is often quite large compared to the other irregularities in the bore. The increase in bore diameter is close to
1 mm (from ~19 to ~20 mm) over a distance of around 20 mm. It would not surprise me if this had a significant effect on the tuning of some notes.
I'm curious to hear what the model has to say about the effect of filling this cavity, which is essentially what you do when you make a longer head for
an antique flute so that the slide does not need to be extended as far.

The other interesting thing I discovered while looking for data to send to Tunborough was a bore profile graph of a flute I have that was made by Wylde.
Its bore profile looks just like the one Terry posted earlier for his R&R 5501, complete with some evidence of compression at the top tenon and
those two very pronounced corner shaped cavities at the joints between the body sections and lower body and foot. I'm pretty sure those latter two
kinks are the result of reverse reaming at the bottom end of the two body sections, because there is no compression before them and the bore diameter
actually increases (as you travel toward the foot). They are quite different to the compression on the top tenon, which looks like it could be a thread
strangulation effect to me.

[Tunborough]

I've received paddler's measurements. It will likely take me a while to report back with anything; I've got some Christmas wrapping to get out of the way.

I'll look at what impact the cavity left by the tuning slide might have on tuning.

[Tunborough]

Using this yardstick, lengthening the head wasn't enough to bring the notes on the uncompressed flute into line. Shrinking the holes as Terry suggested came closer (and A4 was close to 430), but that left the second octave relatively sharp. However, without some measurements from the real flute, I'm not sure we can rely on the model at this level of detail.

Duh. This is what happens when you let someone who doesn't know flutes try to model them. If the second octave is sharp, move the stopper.

With the holes shrunk as Terry suggested, and the stopper pulled out another 3 mm, almost all of the notes fell in line at A4=430, except F# was somewhat flat, high G somewhat sharp, and high C-nat and C# about half a semitone flat. I might have done even better with further adjustments to the tuning slide and stopper. So I would guess that the flute was in tune before Nicholson started enlarging the holes.

[Casey Burns]

"Moving the Stopper" is a big issue amongst modern flute players, who like to split hairs. Similar to their head joint selection process in the face of different styles. In the latter, they are trying to make their cylindrically bored flutes (the "parabolicism" of the head joint is still close to a cylinder for all intents and purposes) sound like our reedy sounding taper bored flutes. It will never happen. One can move the plug around on these and its will hardly make a difference in tone and response.

This is hardly the case on taper-bored flutes! I learned early on (confirmed by discussions with other makers back in the early 1980s) that the cork position is more important for setting the tone quality and response of the instrument. Tuning of the octaves is then done via scaling parameters including wall thickness and undercutting, besides simply adjusting the hole position iteratively. In practice the holes should be drilled undersized, resulting in a flat note in the 1st octave. It should be enlarged until it is in tune. The 2nd octave will be flat at this point and this note is improved by undercutting the hole. The shaping of the hole (straight conical or flaring/biased etc.) can also make a difference in tone and response. One needs to know where to stop in both steps and this is best learned by trial and error and much practice. After some 4000 flutes I am still learning!

I usually set my plugs around 24 to 25mm from the center of the embouchure. People commonly think that these must be at 19mm since that is the apparent standard in modern flutes. I forget where Rockstro and other 19th century flute authors recommended for these original flutes. Much of this is an orthodoxy that I have never subscribed to.

Casey

[paddler]

With the holes shrunk as Terry suggested, and the stopper pulled out another 3 mm, almost all of the notes fell in line at A4=430, except F# was somewhat flat, high G somewhat sharp, and high C-nat and C# about half a semitone flat. I might have done even better with further adjustments to the tuning slide and stopper. So I would guess that the flute was in tune before Nicholson started enlarging the holes.

That is good news. I think it provides strong evidence in favor of our theories. The body tuning of the flute was originally designed for a lower pitch standard, despite being given the ability to play higher by shortening the head and lengthening the tuning slide extension, and louder/brighter by enlarging the tone holes. When you shorten the head and open the slide in order to play in tune at A=430 hz, and then later compress the slide in order to play at A=440 hz it is expected that it throws the tuning out. Also, as many people have commented over the years here, most conical bore flutes need the cork position to be significantly further back than a bore width in order to play well. I have found this to be pretty much universal among dozens of antique flutes I have restored. Often the embouchure to stopper distance has to be opened up quite a long way in order to bring the octaves in tune with each other.

So, I am encouraged by these results. They seem to explain most of the major tuning anomalies. And, of course, it lends support to the theory that flute makers of the past did know how to make flutes that were in tune with themselves! Duh!

It will be interesting to look into the effects of bore profile changes, such as closing the cavity that is opened by extending the tuning slide, opening the compressed areas that may be restrictions due to thread strangulation, closing the cavities caused by back reaming, and smoothing the steps caused by reaming errors or non-standard deterioration across adjacent flute sections etc.

[Terry McGee]

Hi all

Sorry for the protracted radio-silence - I've been out-of-town on carillon business, and now of course there are reports to write and invoices to submit, so I'll have to keep head down and tail up for a bit yet. Bells are going to be big in Australia in the year to come - we have two out of our three carillons being upgraded to modern specifications, which is 50 year step up for one of them and an 85 year step up for the other! And since I'm the resident expert, it's not easy to duck for cover. (It's not hard being the resident expert when you are also the only person in the country working on carillons!)

So yeah, those results are encouraging, although we should regard them as preliminary until we can actually model such a flute accurately and in greater detail. Let's definitely come back to that later.

Great that you're providing some real data, Paddler, and yes, I'd love a copy so I can keep across the discussions arising.

Tunborough, I imagine you're also aware of Paul Dickens' work at UNSW? I was one of the "industrial partners" in that project.

(http://newt.phys.unsw.edu.au/~pdickens/

[Tunborough]

Bells are going to be big in Australia in the year to come - we have two out of our three carillons being upgraded to modern specifications, which is 50 year step up for one of them and an 85 year step up for the other! And since I'm the resident expert, it's not easy to duck for cover. (It's not hard being the resident expert when you are also the only person in the country working on carillons!)

Cool. But only 85 years? I attended a fascinating talk by Miguel Carvalho, et al., at ISMA 2017. They were refurbishing the Mafra carillons in Portugal, which are almost 400 years old. Because of the historic value of the bells, they had to find non-invasive ways to restore the bells.

Tunborough, I imagine you're also aware of Paul Dickens' work at UNSW? I was one of the "industrial partners" in that project.

(http://newt.phys.unsw.edu.au/~pdickens/

Yes, I read his thesis when I was working on the whistle model. Might be worth re-visiting now that we're looking closer at our flute model. I think we're looking for a mouthpiece model that uses more detailed information about the mouthpiece geometry and stopper position than Paul was using at the time.

[Lsu]

Casey,
I certainly agree with your comments. In my experience, moving the head cork up to 5 mm in either direction only affects pitch slightly while it does a great deal of work on tone. I find myself adjusting the cork almost daily for tonal purposes depending on the mood my embouchure is in that day (which I'm sure is bad practice for embouchure training)

[Terry McGee]

Bells are going to be big in Australia in the year to come - we have two out of our three carillons being upgraded to modern specifications, which is 50 year step up for one of them and an 85 year step up for the other! And since I'm the resident expert, it's not easy to duck for cover. (It's not hard being the resident expert when you are also the only person in the country working on carillons!)

Cool. But only 85 years? I attended a fascinating talk by Miguel Carvalho, et al., at ISMA 2017. They were refurbishing the Mafra carillons in Portugal, which are almost 400 years old. Because of the historic value of the bells, they had to find non-invasive ways to restore the bells.

This is a young country (in terms of European settlement. In terms of Aboriginal settlement, it's a really old country!). Our first two carillons were War Memorial carillons. Many Australians fought and died in Europe in the Great War, and hearing carillons was a common experience for Diggers (as they called themselves) over there. The third (the one I routinely service) was a gift from the British people to Canberra for it's 50th birthday. Heh heh, it was accepted "on behalf of her Australian subjects" by the Queen. How weird is that?