No one event probably changed
the course of in flute history more than Boehm's invention of his new
cylindrical bore. The new instrument wasn't to everyone's
satisfaction of course, then or now, but it has to be recognised as a
remarkable feat. But while everyone knows that the flute itself as
being cylindrical, the finer details of what happens in the head are not
so well known. Despite the head being the engine room of the new
design, it has received very little discussion, and much of that small
amount of discussion has been vague, confusing and sometimes downright
misleading. I thought a bit of actual data from real-life examples
might be helpful.
The data is presented in
graphical form to illustrate the old maxim - there is more than one way
to skin a cat, or ream a flute. Unfortunately for such an
interesting topic, I haven't a lot of time on my hands at the moment, so
I'll confine myself to the bigger issues, in the eternal hope that one
day I'll have time to get back to the finer details.
Most of the data presented
below is taken by me of flutes that either I own or that have passed
through my hands for repair. Any others probably came from
It's fair to say we can break
the head up into three segments:
The tuning slide and
region directly behind that
The tapered central section,
The stopper and region beyond
Useful to note that the stopper
region starts about when the bore gets down to around 17mm. The
embouchure is about 17mm left of that.
Tuning slide region
Boehm flutes always seem to have a tuning slide, and by
definition, tuning slides have to be cylindrical. We can expect
therefore to find the first 50mm or so (starting at the open end of the
tuning slide) to be cylindrical. The graph above confirms that in most
cases, although there are a couple that appear otherwise. I suspect
these tubes were simply warped a little, and that whoever measured them did
not take that into account.
Jumping to the other end, we can see three different
Continue to taper downwards (the yellow trace).
This requires the stopper to be tapered also, and means it cannot be
freely adjusted over a wide range. Not that that presents much of
a problem. It does mean that the stopper has to be installed and
ejected out via the tuning slide end of the head.
Become cylindrical at around 17mm. Probably the
most popular approach, and the most practical. Stoppers work well
and can come out either way.
Backreamed. Two examples show the end of the head
backreamed using probably the same reamer as used for the central
Tapered Central Section
Now we come to the crux of the matter, and I'll repeat the
chart for convenience:
You can see most of the flutes measured followed the same
form with only very minor variation. Only three stand out
the sudden reduction in diameter of Rudall Carte #2443
at the end of the slide section. this might be due to a wood
The Moon flute which leaves its run about 20mm later,
but then follows the same curve, and
The Clinton flute that seems the only one to have a
different taper. I probably need to investigate why.
Of these three sections, it's the taper that is the most
significant acoustically, and the least well understood. As you can
see, it is not a straight taper, but neither does it really look like a
parabola. If you hold a piece of paper up to the screen such that it
crosses the end of the tuning slide section and the start of the stopper
section, you'll see that the bore forms a curve between those two points,
with the centre of the curve passing through a point about 0.2mm higher than
a straight line would do. Using the University of New South Wales
flute model, I can see differences in tuning when I move the middle of the
taper by this amount, so we can probably assume Boehm could too.
Hopefully, you'll find the data and explanations above of
interest and maybe help in your work. Clearly, there are some
unanswered questions that hopefully one day we can get back to.