Well, about now, we need to
sit back, absorb all we've found and wonder what it all means!
Not just the top tenon...
I've been concentrating
in this article on the top tenons of all these flutes, probably because
it's that tenon that has the most profound effects. A constriction
at this point of the flute will effect all the notes, but in different
directions and to differing degrees. Constrictions in the lower
tenons will mostly impact on notes there and lower.
But it needs to be remembered
that most of these flutes are also constricted where the LH meets the
right, and where the body meets the foot. So we can expect more
disruption to tuning and, in the more strangled cases, to performance.
Compression at the lower
actually easier to detect, as it forms a single point of inflection,
rather than two. There is also no chamber formed, until you plug
in the mating section.
Now, let's just imagine that
the test tenon on our make-believe flute had suffered the kind of
distortions we've seen above. It had started out with a thread
wrap of 20.6mm, which would have been exactly what it needed for a nice
snug fit in the socket. But that wrap has now reduced to 20.25mm
in diameter, 0.35mm too small for a snug wrap. Indeed, well before
this stage, the joint would be sliding about uncontrollably, and even
leaking. So what would we do about that? Put on 0.35mm more thread
of course, or perhaps even remove the old thread and start again.
Either way, we now have a tight grip on the tenon again, and an even
stronger band of thread. The game starts over!
Remember my Rudall Carte we
met right at the top? Black thread covered by some additional
white thread. Only mild compression so far, but clearly we're on
Isn't it one of those cruel
ironies that, the more you look after your flute, lovingly changing or
augmenting the lapping when it gets a bit loose, the more likely you
are to kill it! I'm reminded of Oscar Wilde's terrifying poem
the Ballad of Reading Goal. "Yet each man kills the thing he
loves..." Indeed, the very benefit touted for strung flutes, that
seasonal variation can be taken up by the owner, might in fact be the
invitation into the strangulation cycle.
The Good Old Days?
Was it better in the Good Old
Days? Some have suggested that perhaps threads were softer then.
Glancing at the graph at the top though seems to dispel that hope.
The most damaged bores were flutes from the 18th and 19th centuries, and
the baroque instruments in particular would not have seen much if any
use until the Early Music Revival in the 1970's. By then the
Schuchart was in museum hands, yet it it one of the most damaged.
The Richard Potter is missing several keys, and has probably not been
played for 100 years or more. There was nothing soft about the
thread I took off it.
Imagine this ghastly scenario. A well-intentioned modern flute
maker faithfully copies a period flute without making allowance for the
thread-induced bore compression. So the copy is also distorted.
But then the maker also uses thread to wrap the copy's tenons.
After some time, it starts to work its ugly magic, and the copy is now
more distorted than the original! I'm told it happens regularly in
the early flute field. Perhaps it happens in our field too?
Clearly, we must understand bore compression and take
steps to guard against it.
What about re-reaming?
Some have suggested that a flute displaying signs of
constriction should simply be re-reamed to remove the offending
A moment's thought though should ring warning bells. When you ream
off the protrusion into the bore, you're further weakening the tenon
wall. Carry on like that - putting more thread on the outside and
reaming off the wood on the inside - and the two will finally meet.
Probably with a bang!
A cause for instability?
Sometimes you come across
flutes (and not just old ones) where one or more notes are unstable.
This can take several forms, but a common one is a warble, probably
caused by the vibrating air column vacillating between two competing
resonances. It strikes me that, given the nature and degree of
tuning change the computer modelling suggests is likely, that
strangulation could easily shift the modes enough to create instability
problems where none previously existed. Could be a good thing to
keep in the back of the mind to check for the next time one comes across
such a case.
Hard D rehardened?
One of the noticeable
improvements on the performance of the strangled cocus flute was a very
significant improvement to bottom D. Where it had been really
quite wuzzy, it was now crisp, focussed and strong. Yet the computer model
predicts very little effect on the D notes (see graph reproduced below).
How could this be?
Bottom D is a note rich in
harmonics, as we confirmed in
Investigations - Analysing an existing recording, and you can prove
easily to yourself. Finger xxx xxx, you should be able to blow the
harmonic series D4 (low D), D5, A5, and D6 quite easily. By
comparison, how many harmonics can you blow on xxo ooo?
Further, in the Irish style
of playing, as we discussed in
Getting the hard, dark tone, we purposefully shift the energy away
from the weak fundamental note (low D) and into its harmonics to give
the illusion of the piper's "hard" D. But that's only going to
work if all the harmonics are in good tune. Indeed, if they are
not, they are not harmonics, by definition, but rogue resonances.
If not in tune, they fail to coordinate the return of their contribution
to the pressure wave back to the embouchure hole, and jet switching
The modelling predicts that
the D notes would be unchanged by the strangled bore under the tenon,
but the third harmonic, A5 is near the peak of the affected notes.
Twenty-odd cents flat is probably enough to pull the contribution of the
third harmonic out of the mix (we have more work to do to define the
acceptable window, but 20 cents is probably close, and that really means
within +/-10 cents, depending on how accurately the window was installed
in the first place).
To confirm the importance of
the third harmonic in the mix, check out the analysis below of notes
played by the late Paul Davies in the Lament of the Three Maries.
D4 is the navy blue trace. You'll see that the fundamental (D4) in
the H1 column is down at about -17dB. Very weak. But the 2nd
and 3rd harmonics (D5 and A5) are up at -4dB. They are shouldering
the bulk of the load. The 4th harmonic (D6 - our high D), is down
at -10dB and it's all downhill after that. So, if strangulation
can dramatically diminish the support of the equal front runner, no
wonder our low D is in some trouble!
Let me say that this
hypothesis needs to be further tested before we can rely on it.
I did test it on Prof. Neville Fletcher, who responded that it sounded
"exactly right" to him. Encouraging! It does seem to fit the facts, and to explain the
prima facie paradox
between the modelling and reality. The current version of the
computer model does not allow for viewing harmonic coincidence, but it's
high on my wishlist, for obvious reasons. It could offer a far
glimpse into the invisible workings of the flute.
There are important
ramifications of this observation:
it may explain why many
old flutes still do not have a satisfactory low D even after ruling
out all the other possible culprits - leaking pads, misplaced
stoppers, badly cut embouchures, etc. Testing for bore
compression, and being able to do something about it, become part of
the restorer's job description.
What applies to low D
will probably apply to notes nearby.
We need to keep in mind
the contributions made by the harmonics when applying computer
modelling to performance issues. This will be made easier,
indeed semi-automatic, when a means for viewing the harmonic
alignment is built into the modelling.
What applies to the top
tenon strangulation may apply to strangulation of the other tenons,
but will have its influence elsewhere in the flute range. We
can use computer modelling to identify the likely places to
look, then before-and-after RTTA to confirm.
Strangulation might be an
appropriate term for a murderous constriction just below the head,
but is less apt for constrictions around the middle and just above
the foot. I need some new terminology!
This issue could apply to
new flutes too, where the new design is based on an original with
it might mean that a
better home-test for strangulation might be acoustic rather than
measurement-based. Identify those notes most likely to be
affected by compression under each tenon and test them.
Computer modelling will suggest them to us, but we need to confirm
the results in the real world.
Aha, a mystery explained?
Every now and then, the
restorer or repairer is confronted by an intriguing mystery. An
old flute with two or more sections joined together inseparably.
The joined sections are free to rotate, but will not pull apart.
What clearly has happened is that the entire thread-band has "glued"
itself to the inside of the socket, but separated itself from the bottom
of the thread trough it was originally wrapped around. The tenon
can rotate inside the thread-band, sometimes very freely, but cannot be
It's not hard to imagine why
two parts of a flute may get jammed together, but it hasn't been clear
why one of them is able to rotate freely inside the other. Now we can see
Imagine a flute has been
played for some good time, is thoroughly wet inside, and the owner has
tumbled into bed without pulling it apart and mopping out. (Obviously, the flute
had to be left together for the parts to become so firmly attached.)
During the night, the moisture continues to soak into the tenon,
swelling it further and further, expanding the thread band as much as
its limited elasticity will allow and pressing it all the more firmly to
the inside of the socket. Perhaps the wood shoulders at the sides
of the thread band are also swollen enough to jam them against the
inside of the socket. Whatever, in the morning, the flute owner
finds the flute thoroughly jammed and has little choice other than to
leave it some days for the swelling to abate.
Unfortunately, the outer
layer of thread really adheres firmly to the inside of the socket,
possibly for a number of reasons. Perhaps breath condensate is
acting as a glue. Or whatever oil or finish has been applied to
inside the socket is the adhesive. Or something that has been
applied to the thread to improve its water resistance or to make
assembly easier. Or an unfortunate combination. Whatever,
the thread forms a permanent attachment.
But now here's the
interesting bit. Finally, the flute dries out and the tenon
shrinks. The crushed tenon wood now releases its
attachment to the inside of the thread band, but the thread-band
remains adhered to the socket. The joint with the tenon is now
free to rotate within the thread band, but is not free to be withdrawn.
The same action that crushes our tenon, and causes strangulation of
the bore, is what separates the thread band from the bottom of the
thread trough. It will be interesting to check the next
jammed-but-rotating flute for bore compression!
Follow up: I've just removed
the thread from the lower end of the Richard Potter flute. The
outside of the very old thread was very compressed - indeed polished and
shiny. But, as I started to remove it, I became aware that the
rest of the thread was loose in the trough - I could rotate it very
easily. This confirms the mechanism above - the tenon wood had
expanded as far as the thread would let it, when wet, and then retreated
as it dried out, leaving the thread pressed outwards. Most
To summarise, let me advance
this analysis. For tenon-wrapping (cork or thread) to work it must
just firmly fill the void between the socket and the tenon. Any
less and it will leak or not hold the flute together satisfactorily.
Any more and it will put unacceptable outward pressure on the thin wood
of the socket. But the tenon wood is going to get wet during
playing, and will want to expand. If the tenon wrap is
thick-enough cork, it will have that room, provided by the resiliency of
the cork. But if it is thread it will not, and the wood of the
tenon will be compressed. Even if the thread wrapping is applied
loosely, it will be compacted by the same expansion-contraction
wetting-drying cycle, until more thread is needed to secure and seal.
Once enough thread is applied, the pressure goes onto the wood. How can
it be any different?