An Improved Tuning Slide for the Irish Flute



Flutes can be made, like recorders, without a tuning slide.  The small amount of tuning which is necessary can usually be accomplished by withdrawing the headjoint slightly at the first tenon.  Tuning slides are handy however:

  • you have a wider range of tuning available to cater for hot or cold venues, moist and dry days, players who play further into or further over the embouchure hole, errantly tuned pianos in pubs, sharp Uillean pipes, etc.
  • adjustments to pitch can be made more easily on the run, as the slide, when working properly, is very smooth in operation. This contrasts with the alternative, pulling the headjoint out at the first cork-lapped joint, which tends to be more "grabby".
  • pulling out the slide produces only a minor variation (5%) in bore diameter at that point, compared with the larger discontinuity (24%) produced by pulling out at the socket.  This brings benefits in terms of tuning and efficiency.

What's wrong with the old tuning slides?

The original 19th century wooden flutes were fitted with internal thin brass liners to the head and barrel. These telescope together at the joint, providing a tuning slide. There are advantages and disadvantages to this system.

The advantages include:

  • the liners prevent moisture from the breath soaking into the wood. (This applies only to the head and barrel, the rest of the flute being unlined anyway.)

The major disadvantages with the old system are:

  • that inevitably (or at least 99% inevitably) any wooden flute head and barrel with an internal metal lining will split. Wood shrinks with age and metal doesn't.  Bang! Almost every old lined flute I've seen (and an increasing number of recent ones) has cracks in the head and/or barrel. These are also cracks that are difficult to repair reliably and nicely.

  • that the presence of metal in or near the embouchure hole can detract from the sound of the instrument. While the maker no doubt put a lot of effort into smoothing the junction between wood and metal at the bottom of the embouchure chimney, differential expansion rates can mean that the metal juts into the airstream, causing vortices and resultant noise and roughness at the discontinuities.

What about partial liners?

Some flutes, particularly French ones, have only partial liners, and it is sometimes suggested that this is the solution for modern flutes.  But, alas no, partially lined flutes suffer partial cracks, as this early 19th century Gerock flute illustrates.  The slide here only extends to where the crack ends - the wood above the end of the slide remaining intact, as you can see.

The moral is obvious - wood must not be lined with metal or anything else that will resist the natural movement of the wood during variations in humidity.

My policy

It has never seemed right to me as a maker to perpetuate these problems, and so I have always tried to steer buyers away from traditional tuning slides. Cracking is the major issue, especially given that there is no reason why a well made instrument should not still be in use hundreds of years later. Paradoxically most 19th century flutes in museums are cracked in both head and barrel.  Most 18th century flutes (before the tuning slide was invented) aren't.  Who wants to make (or buy?) an instrument which may render itself unplayable in one to ten years?  I want to make instruments that will be handed down and played for centuries!

It won't happen to me!

How do you know if this is likely to affect you?  Your climate is the guide.  Will your instrument experience very dry weather for more than a week at any time in the year?  Answer yes if you live in a very dry place.  Answer yes also if it gets very cold in winter and particularly if it snows or if you have central heating.  Answer yes if you have air conditioning in summer.  In fact, answer yes unless you live in a climate that is medium to moist all year round!

Ummm, how moist?

The Royal College of Furniture, London, recommends that timber for musical instrument purposes should be seasoned to an Equilibrium Moisture Content (EMC) of 12%.  (These are figures from the 1980's - the RCM's successor is likely to recommend drier figures these days, consistent with the increasing use of central heating and air conditioning.  The 1980's figures will be closer to the 1850's reality.)

This moisture content equilibrates to a relative humidity in the air of about 65%. Compare these other recommendations to see where you might fit in:

  • 16% UK outside furniture [80%]
  • 12-14% Occasionally heated rooms (UK) [70%]
  • 11-13% Normally heated rooms (UK) [65%]
  • 9-11% Continuously centrally heated rooms (UK) [55%]
  • 9-11% General level for southern and coastal regions of USA [55%]
  • 8% Most northern and central regions of USA [40%]
  • 6-8% Radiator shelves and arid south west of USA. [35%]

(the leading figures are EMC, the figures in [] are the equivalent %RH in the air.

From this we can see that 19th century instruments, probably made in occasionally heated or normally heated rooms in the UK should be kept humidified to 65%RH or more.  And if you live in the US, you can see from the lower part of the table how much drier your climate is.  Modern instruments made in the UK or Eire can be expected to have similar requirements for care.

A Way Forward

But does it have to be like this?  Can't we have the benefits of the tuning slide without its attendant problems?  At last, yes!  But expect a few iterations along the way...

The New Improved Tuning Slide Mark I

This was a complete rethink of the tuning slide issue and, I believe, a new development, perhaps the first real development in the eight key flute since the days of the old London makers. With the Mark I slide, no part of the slide is encased in wood, so cracking through shrinkage is entirely eliminated. 

The slide goes nowhere near the embouchure hole; consequently, I cannot detect anything of the metallic edge to the sound I hear from lined heads. It's hard to be sure, but I believe the sound is indistinguishable from my unlined heads.

Silver Mark I slide on a blackwood flute

The slide is made from hard drawn sterling silver and is thus sturdy and smooth in operation.

The slide also brings other benefits. Because the usual wooden barrel socket is replaced by a metal socket, the joint comes together and apart very smoothly. This socket is much stronger and thinner. This means that the upper tenon on the middle joint can be thicker - this tenon is weak in the old flute. Further, the thickness of the upper part of the midjoint can be reduced, making the flute more comfortable to hold in the left hand.

So the Mark I slide is more than just a slide, it brings a new look and new functionality to the eight key flute.

The New Improved Tuning Slide Mark II

For those wishing to retain the old flute look, I developed the New Improved Tuning Slide Mark II.  It looks identical to the traditional tuning slide.  Whereas the traditional slide completely lined the head and barrel, the Mark II only enters 20mm (3/4") into each.  This in itself is not enough to prevent cracking - plenty of old and new flutes have partial slides and have cracked at these points.

Instead of being held fast by the wood, the new slides are lapped in tenon cork, and in fact can be removed if they need attention.  The resilient layer of cork permits the wood to move with the seasons without creating the kind of stresses needed to crack it.

The tubes of the Mark II slide are made by the traditional seamed method, hammered round on mandrels; the inner tube being then turned and polished to fit the outer.

The New Improved Tuning Slide Mark III

This is a variation on the Mark II slide and retains its strategies to beat cracking. Instead of the outer slide being a solid tube of sterling silver, it is now a brass tube with a solid sterling silver cover in the part visible in the gap between head and barrel. This offers several advantages over a solid tube of silver:

  • a slide made of dissimilar metals runs very smoothly

  • brass can be hand-reamed for the finest fit

  • I can use specially hard-drawn seamless tubing for all parts

The Mark III slide looks identical to the Mk II and to the 19th century slides, except that the inner tube is silver, whereas the 19th century flutes used nickel plated brass.

And now ... the New Improved Tuning Slide Mk IV

This is essentially identical with the previous Mk II slide, apart from its mode of construction.  It takes the ultimately simple form of two hard-drawn silver tubes.  A new process, termed "fluid force", forms the tubes from sterling silver slugs.  Benefits are:

  • elegant simplicity - only two parts

  • both tubes are seamless

  • all sterling silver to minimise corrosion

  • extremely hard-drawn to minimise wear and damage

  • uniformity of size permits interchange of heads

The appearance of the finished instrument is the same as in the image above.  The internal structure is shown in the sketch below.

It can be seen that the two silver slides only partially line the head and barrel, and are buffered from the wood by a layer of tenon-cork.  This is the important part, permitting the wood to swell and contract with changes in humidity.


Players with my (or indeed any maker's) previously unlined heads can opt to have the new slide "retro-fitted". As this will make use of the original head, there will be no breaking-in period involved.

Maintaining the New Improved Tuning Slide

Should the slide become tightened through damage or loose through wear, it can be adjusted by any woodwind repairer using the standard Boehm flute head swedging and expanding tools.  Like any slide, it's important to clean off any breath condensate from time to time, and to lubricate the metal with a little cork grease or similar substance.

Because the embouchure area of the headjoint remains unlined, players will still have to mop out their headjoints after playing (which you should do anyway even with a lined joint to prevent corrosion forming and bacteria growing!). The wooden section will also require oiling periodically. This is the same as for an unlined head and for the rest of the instrument of either type.

Other Makers:

I do not claim these to be the only or best solutions to the tuning slide question - but they are perfectly satisfactory ones.  I do assert that continuing to use the old style tuning slide will, sooner or later, mean that your work will suffer cracks which are hard to repair elegantly and which, it can now be seen, are preventable.

I am quite happy for other makers to adopt my designs for their own instruments asking only that they acknowledge them as 'Terry McGee's "new improved tuning slide"' or something similar.  In the same way, I'm keen to hear of and acknowledge any developments to the eight key flute that you might make.  This way, the eight key flute will cease to be seen as just the primitive predecessor to the Boehm flute and will be seen for what it is - a different and equally valid instrument following its own developmental path.

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Created: 11 June 2001