tone hole undercut

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monkeraimac
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tone hole undercut

Post by monkeraimac » Sat Dec 11, 2010 10:12 pm

Could some one advise me on the practice of undecutting tone holes on a new chanter and what effect it will have. I just roughed out a quick chanter to practice tuning up on before attempting on good chanter any replies very welcome thanking you in advance monkeraimac
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Mr.Gumby
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Re: tone hole undercut

Post by Mr.Gumby » Sun Dec 12, 2010 4:22 am

The whole fine tuning and voicing of a chanter is based on the way it's undercut. I think you may be underestimating it's importance.
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monkeraimac
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Re: tone hole undercut

Post by monkeraimac » Sun Dec 12, 2010 7:13 am

no didnt underestimate the importance of it just needed a bit of guidance as to where to start didnt want to blaze away at several days work with no idea were to start the process im in a very isolated piperless area and there 's not much info out there on doing it other than the forum so im still hoping for a bit of help many thanks in advance.. monkeraimac
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djm
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Re: tone hole undercut

Post by djm » Sun Dec 12, 2010 7:34 am

I think you will get your best answers from the pipemakers here, but the basic idea is that if you undercut at the top of a tonehole you are raising the position of the tonehole on the chanter, and if you undercut the bottom of the tonehole you are lowering the note. But also you must note that you are changing the inside of the bore a bit each time, so each hole you modify can affect the others. Very touchy stuff, and a quick way to trash the chanter. That's why non-makers are discouraged from tuning their chanters by undercutting. Modify the reed before trying to modify the chanter.

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Mr.Gumby
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Re: tone hole undercut

Post by Mr.Gumby » Sun Dec 12, 2010 11:40 am

Maybe I should have said (and I think I did initially, I deleted some of what I had originally written) 'underestimate the complexity and delicacy of the process with regards to tonality how it affects fingerings to colour your tone as well as the effects on tuning'.

Rounding edges in the chimney will reduce turbulence, which is important. The size of the holes and how much they are undercut (and in which directions) affect tuning and how your chanter responds to cross fingerings to alter pitch and colour of a note. A small scrape can have a broad effect.

Geoff Wooff's articles in Ceol na hÉirreann vols 1 and 2 should be more helpful and detailed than what you'll find on an internet forum.
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outofthebox
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Re: tone hole undercut

Post by outofthebox » Mon Dec 13, 2010 6:38 am

This is interesting. It seems to me that a maker might fine tune a new chanter to a pre-existing reed which is known to be right, because it plays well in the model chanter. The new chanter would be bored to play all notes flat and then brought up to the required pitch by fine incremental undercutting - a little bit off here and a little bit off there - checking the effect on tuning after every adjustment. Given the difficulties associated with long bore lathe work, the bore of the new chanter is unlikely to measure precisely the same as that of the model chanter, so the nature of the undercutting required will also be different. In an ideal world it might be possible to reproduce an exact copy of the model chanter. But the possibility exists that the experimental undercutting approach may in the end produce a new finished chanter which is superior to the model. So the quest continues 8)

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Re: tone hole undercut

Post by Mr.Gumby » Mon Dec 13, 2010 10:10 am

You make it sound like undercutting is some sort of crutch. You obviously did not take on board what I wrote. So I'll say it again: Undercutting is an essential and crucial part of chanter making used by the great pipemakers like Coyne, Egan, Harrington etc. It's an essential method for voicing a chanter.
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LiamO'Flynn
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Re: tone hole undercut

Post by LiamO'Flynn » Mon Dec 13, 2010 1:21 pm

Mr.Gumby wrote: You obviously did not take on board what I wrote.
Considering you,re not a pipemaker why should he,
There are two schools of thought on this subject ,one says undercutting tone holes is important,the other says not. In this case you have to try it and come up with your own conclusions.

Liam
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bobble991
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Re: tone hole undercut

Post by bobble991 » Mon Dec 13, 2010 2:33 pm

I think the point here is he wants to try it and is looking for a little guidance on how best to tackle the job. I too would be very interested is any replies as for me it is currently, to paraphrase someone else, the final frontier and I would like to boldly go........ :D

Bob

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Re: tone hole undercut

Post by LiamO'Flynn » Mon Dec 13, 2010 2:54 pm

The first question you have to ask is, when you have made your basic chanter and have fitted a good reed ,what does the chanter need. 1# is the chanter in tune.2# how does it sound and is it responsive to the level you think it should be.3# how does it feel.

Liam
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Mr.Gumby
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Re: tone hole undercut

Post by Mr.Gumby » Mon Dec 13, 2010 3:33 pm

Considering you,re not a pipemaker why should he
No, I am not a pipemaker. But I have played probably dozens of chanters in a pipemaker's workshop that were in the process of being voiced. So with my testdriver's hat on I think I have a bit of experience I can speak from with regards to the effect of undercutting. But I'll shut up, work away among yourselves lads.
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LiamO'Flynn
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Re: tone hole undercut

Post by LiamO'Flynn » Mon Dec 13, 2010 4:14 pm

Mr.Gumby wrote: So with my testdriver's hat on I think I have a bit of experience I can speak from with regards to the effect of undercutting. .
Ok then tell us about the effects of undercutting ,how its done and so on.

Liam
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billh
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Re: tone hole undercut

Post by billh » Mon Dec 13, 2010 4:41 pm

As usual, noise wins over answers to a good question. :-(

There are, broadly speaking, two sorts of tonehole refinement which are commonly referred to as "undercutting". One could be considered a relatively subtle rounding of tonehole edges. As Mr G pointed out, this reduces turbulence, and is thus a desirable thing to do. There is at least a consensus on this point among professional makers of other woodwinds, since Arthur Benade's time at least. The benefits of reduced turbulence are generally given as increased responsiveness, improved tone, and increased stability (resistance to squeaks, squawks, and notes that speak more easily).

There may not be a consensus about anything at all, in the world of uilleann pipes (that goes for makers, players, and spectators of all stripes).

However a majority of makers do round tonehole edges to some extent. Besides the effect on turbulence, rounding toneholes can subtly cause a tonehole to "act" larger.

The second type of "undercutting" involves more than reducing eddies/turbulence in the vicinity of an edge. To explain what it changes, consider several things: the "pressure node" (i.e. the place where the standing wave in a chanter effectively 'ends', when a tonehole is open) is located some distance _past_ the open hole; that is to say, the pressure modulation of the standing wave does not abruptly end at the tonehole, but extends outwards for some distance. The size of the hole has a strong effect on this distance - thus a smaller hole produces a flatter note, since the _equivalent_ or _effective_ position of the node is farther away from the instrument. The larger the hole, the more rapidly one approximates "open air" conditions as one moves away from the bore's air column. This effect of hole size to "effective" standing wave length is sometimes referred to by a "tonehole length correction factor" - approximating the additional length one must add to the physical bore length in order to estimate the standing wave length behavior actually observed. Undercutting the hole causes it to "act" bigger, both in the sense that it smooths the transition between bore and "atmosphere", and in the sense that it literally does make the hole larger as a three-dimensional entity. For similar reasons, scalloping the outside of a chanter makes the holes "act" larger by reducing the chimney heights and thus reducing the ability of the tonehole column to support big pressure drops. Undercutting is, in this way, something like inside-out scalloping, in that it has a similar effect on the chimney height.

Of course extreme scalloping in one direction or the other, for instance undercutting at the top of the tonehole but not the bottom, does have the effect of shifting the effective center of the tonehole, but I do not think that this is a particularly significant aspect of what's going on, and I don't think it sheds much conceptual light on what's going on. If a tonehole gets larger when being undercut down, the fact that the centroid of the tonehole is shifted towards the bell does not, in general, produce a flatter note - since the effect is to make the tonehole larger, not "lower". By analogy, think of an exit door... if you enlarge the exit to a building in the direction _away_ from the entrance, people will still be able to get out faster even though the "center" of the door has been moved farther away.

That said, undercutting upwards and downwards will usually give different results, but because the two tonehole shapes have a different balance between the "sharpening by moving the tonehole" effect and the "sharpening by enlarging the tonehole" effects. Note also that the relationship between tonehole size and "length correction factor" depends on frequency, which means that it will affect the two octaves differently. Undercutting also affects the "cutoff frequency" for sound radiated by the toneholes - again generally making them "act" a bit larger.

In addition to influencing the transition from bore standing wave to "open air" node, the "chimneys" which are formed by the non-zero thickness of the chanter have another effect. These little chimneys of air can act like "dampers" which suck energy from the standing wave itself. In this way they can flatten notes below, and impact tone (perhaps dulling it, or in other cases killing an undesirable resonance and thus "warming" the tone). Rounding the tonehole edges on the inside seems to reduce the damping effect, thus reducing the flattening and dulling effect on notes below - acoustic physics predicts that this should be so and it does seem to work.

At the same time, undercutting has the effect of enlarging the bore at the location of the tonehole (or rather, just above and/or below the tonehole). This also tends to sharpen the corresponding note and, generally, the note immediately below it as well, like any bore enlargement. It is expected to affect all notes below the undercutting, on the chanter - possibly flattening some and sharpening others, depending on whether the expansion is located at a pressure node or antinode for the standing wave frequencies in question.

Very approximately, one can speak of various undercutting, rounding, and scalloping techniques as altering the "effective diameter" of the toneholes, and possibly slightly impacting their effective "position". For expediency's sake, or perhaps from other motivations, some people have taken the view that one should aspire to perfectly round toneholes, devoid of scalloping or undercutting, placed in the "equivalent" position to achieve the approximate "size" behavior that could otherwise have been achieved via undercutting; possibly with some minimal rounding of sharp edges, if the turbulence effect is accepted as valid. This point of view relies on an approximation rather than a fact - an undercut tonehole does not have an exact "equivalent" round size or position which applies to both octaves and which has the same tonal effect.

Further, our biggest tuning conundrums result from the fact that, unlike almost all other woodwinds, the bell of our chanter does not in general open up to free air, nor are all the toneholes below the top open one assumed to be open as well. Especially for "one finger" notes played "on the knee", the air column below the open tonehole is still active and capable of supporting a standing wave. The effective length of this secondary bore - one could perhaps call it the "passive bore" - depends strongly on the size and shape of the open tonehole above. (David Quinn and Benedict Koehler call it the "zombie zone" since it's neither dead nor alive...). The actual standing wave behavior in the case of a closed-end chanter is a blend or compromise between the preferred resonances of the two bore regions, which are coupled together and thus must find some cooperative regime of oscillation.

Enlarging the tonehole might be expected to shorten the effective lengths of both bore sections/standing waves, possibly affecting the two octaves to different degrees but sharpening the notes in any instance. However this is not always the case, because the _primary_ impact of enlarging a single open tonehole in a closed chanter is to reduce the relative importance of the 'zombie zone' by weakening the secondary standing wave therein. If the "zombie zone" standing wave wants to be sharper than the "live" region above, the resulting compromise will be a sharper note. In such cases, enlarging the open tonehole may have the paradoxical effect of making the note flatter, by reducing the influence of the (would-be sharpening) zombie wave. This commonly happens with the F# on baritone regulators; many an F# has been needlessly and incorrectly enlarged in an attempt to cure a flat F#, when _reducing_ the F# hole would have done the trick, by increasing the influence of the (sharper) "lower bore resonance". Andreas Rogge sometimes adds a tuning screw to the F# on his baritone regulators to address this very issue, and the "pistons" in some regulator end caps similarly attempt to exploit the impact of the "zombie" region on regulator tuning. You might note that in the case of regulators, every note is a one-hole note with a stopped/closed bore beneath, so these secondary standing waves are very important indeed.

You can assess the influence of the secondary (aka 'zombie') standing wave by taking the chanter off the knee, with a given fingering. In general, if the note gets flatter when lifted, the zombie zone is what's pulling it sharp, whereas if the note gets much sharper off-the-knee, the zombie zone is flattening things. Even a slight change in chanter length (1 or 2 mm) can change the scenario quite a bit. Moving or removing the end caps on a set of regulators can similarly illustrate the impact.

As Mr. G mentions, there's much more to all this than tuning - the effects above do impact tuning but they impact tone very substantially too, and not in one-dimensional ways. Since we want our pipes to respond to a range of different fingerings, with a range of tone colors, while remaining in usable tune with the drones, it's useful to have this wide range of variables at our disposal, even if it seems daunting at times.

Lastly, one key reason for refining toneholes after drilling (and reaming of the chanter) is that, no matter how careful and consistent you attempt to be, every piece of wood will react to the reamers a bit differently. Particularly in the case of small holed "flat" chanters, the final result is very sensitive to subtle tonehole modifications. Shaping the toneholes by hand, empirically, after fabricating the chanter to an ideal plan, give one the wiggle room required to compensate for these differences and allow the individual chanter's potential to emerge - perhaps quite intuitively, without being able to reduce each stage to an explanation. I don't claim to have mastered this process by any means, but I know that it can and does take place.

Bill
Last edited by billh on Wed Dec 15, 2010 10:34 am, edited 1 time in total.

LiamO'Flynn
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Re: tone hole undercut

Post by LiamO'Flynn » Mon Dec 13, 2010 5:39 pm

Regarding Your post Billh which sounds wonderfully technical how do you account for the fact that Davy Stephenson ,who has made some lovely sounding pipes says that voicing is totally unnessesary if the chanter bore and toneholes are made in a way that dont need it.

Liam
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Its a pity nederveen doesn't join in to counteract the Benade point of view !
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Re: tone hole undercut

Post by billh » Mon Dec 13, 2010 5:45 pm

Nederveen agrees as far as I am aware. I will not take the other bait, thank you.

It need not be "technical" if one is prepared to approach the subject with patience and a keen ear. I am sure that a sufficiently dedicated person could learn the technique without anyone else's explanatory notes - but most folks want a quick answer nowadays. I hope that someone, unlike yourself, finds my response useful.

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