THE FLUTE HEADJOINT is perhaps the single most important factor in
determining the flute’s tone quality and responsiveness, given a skilled
player with a mechanically adequate flute.
I own about 20 headjoints, some of them professionally made, but most
left over from my days as an amateur flute headjoint maker in the early
1980’s. Recently, I made an interesting discovery about how bad or
indifferent headjoints (of which I have many!) can be quite remarkably
transformed into good or excellent ones. Even many headjoints that are
good to start with can be noticeably improved. I call this “Acoustic Knife-
Edge Design Element for Improving Flute Headjoints.”
THE KNIFE-EDGE DESIGN ELEMENT is shown schematically in Figure
1. Basically, it is just a way to controllably alter the profile of the “strike
edge,” a critical feature of the embouchure hole. (The strike edge is the
portion of the embouchure hole toward which the player’s air stream is
directed; it divides the air stream into a portion which goes into the
embouchure hole and a portion which goes over the embouchure hole.)
I used the following procedure to construct and install knife-edges:
Starting with a piece of 3M ScotchTM MagicTM Tape (normally 2
mils (0.002”) thick, 3/4” wide, 1” long), I cut out a rectangle having
a width of about 6 mm and a length of about 20 mm, as shown in
Figure 2(A), being careful to leave the original straight edge
(future knife-edge) intact.
This cutout piece of tape forms the “knife-edge assembly.” Its exact
dimensions are not critical; it should be small enough to fit entirely on
the lip plate, and big enough to provide a good contact area with the lip
plate surface. I like to cut the knife-edge assembly to size from a larger
piece of tape (instead of tearing it off the roll) because it gives me better
control over the knife-edge dimensions and fewer fingerprints. However,
if you have narrow tape and a good dispenser, you may be able to get
your knife-edge assembly straight off the roll without any cutting.
I then press-fit the knife-edge assembly into the headjoint lip plate,
positioned as in Figure 2 (B), with an even overhang over the
embouchure hole of about 0.3 to 1 mm. The optimum overhang differed
for each flute headjoint, and was determined empirically. As might be
expected, the best adhesion is obtained with clean, dry lip plates and
WHILE MY INITIAL EXPERIMENTS have focused on home installation
of temporary knife-edges made from ScotchTM MagicTM Tape, one can
also experiment with knife edges of other thicknesses, materials
(different tapes, etc.), shapes (straight, curved, etc.), and degrees of
permanence. More permanent knife-edges could easily be made from
metal, and perhaps could be offered as a factory-installable option for
mass-market student model flutes. It should also be noted that the knife-
edge design element might also be applied to headjoints for other
members of the flute family (e.g., piccolo, alto flute, etc.).
A WORD OF CAUTION: Members of the Editorial Board of The
Flutist Quarterly have expressed concern that application and
removal of tape knife-edges might damage the finish on wood or
plastic piccolo headjoints, or peel off poorly adherent coatings on
metal-plated headjoints. In addition, there was concern that the
sulfur content of rubber electrical tape might damage silver or
silver-plated headjoints. While I myself have experienced no
difficulty in removing ScotchTM MagicTM Tape from my metal flute
headjoints, you should keep these concern in mind and proceed
at your own risk.
IN MY FIRST EXPERIMENTS, I tested MagicTM Tape knife-edges on
several homemade and professional model flute headjoints classified
by me as “being in need of improvement.” The homemade headjoints
were solid nickel-silver or silver-plated nickel-silver, and the
professional headjoints were solid silver. For these headjoints, the
addition of an optimally-positioned knife-edge always resulted in a
noticeably warmer and more focused sound. The improvement was
most dramatic on flute headjoints having overly large embouchure
holes or slightly rounded strike edges. Usually, the optimum knife-edge
overhang was smaller for better quality headjoints.
I NEXT TESTED knife-edges on homemade and professional model
flute headjoints classified as “good” or “excellent.” Improvements to
these higher quality headjoints were more difficult to quantify, in part
because there is no one single paradigm for the “best” flute sound. For
example, some players may prefer a headjoint designed for a
distinctive sound or tone color, while others prefer a more neutral
headjoint which produces different colors more easily by changes in
embouchure. The headjoint best suiting my “tonal ideal” is a Cooper-
style headjoint I selected for its warm sound, fast response, and good
focus (Brannen Bros., 1986). Knife-edge additions on most of my good
and excellent headjoints gave them a sound more like this Cooper-style
headjoint. However, the Cooper-style headjoint was not improved by
the knife edge addition, but rather became slightly stuffy and fuzzier.
USUALLY, too large a knife-edge overhang results in a fuzzier, stuffier
tone, but even with the optimum overhang I sometimes sense an
additional “thinness” in the hight register. I suspect that this thinness is
not intrinsic to the knife-edge design, but rather a result of excessive
tape knife-edge vibration induced by the higher velocity air stream used
to play the upper octave notes. This explanation would predict less high
register thinning with knife-edges constructed from more rigid materials,
and is consistent with my results with a heavier duty 3M ScotchTM
Filament tape. These knife-edges gave a more robust, freer high
register, but at the sacrifice of some lower register warmth.
THESE TAPE KNIFE-EDGES have a finite and somewhat
unpredictable lifetime. A suddenly fuzzier tone in a headjoint that has
previously been working well with a tape knife-edge is a warning sign
that the knife-edge may be starting to life off or peel from the lip plate.
This means that it is time to remove the old knife-edge and install a new
one. While this is easily done at home, it is not something you would
want to be dealing with during a performance. If your tap knife-edge
experiments are giving you a new sound that you want to keep reliably
and / or permanently, it may be time to think seriously about getting a
new, professionally-made headjoint.
Don’t expect too much.
Knife-edge addition may not improve every headjoint, especially
those that are excellent to begin with. Also, a beginner is likely to
sound like a beginner on even the best headjoint.
WHY DOES THE KNIFE-EDGE WORK the way it does? I don’t exactly
know. Headjoint embouchure design is still more of an art than a
science. “First principles” scientific answers are lacking even for basic
questions about embouchure hole dimensions. Why are different sound
produced on oval embouchure holes compared to rounded rectangular
ones? Why are different sound produced by different chimney heights
and different degrees of undercutting? All of these questions have the
same general answer. A change in embouchure hole design changes
the air flow pattern in the vicinity of the embouchure hole, and alters the
details of how this air flow starts oscillating to make the sound waves
you hear as a flute tone.
REMEMBER: While trying this experiment, have fun? At best, you will
get yourself an improved flute headjoint. At the least, you will have
amused yourself while acquiring some instructive hand-on experience
with flute headjoint acoustics.
Katherine L. Saenger is a Research Staff Member at the IBM TJ
Watson Research Center in Yorktown Heights, New York, where
her current (non-flute) research is is the area of electronic
materials. She is a substitute flutist with the Putnam Symphony
Orchestra, a community orchestra based in Carmel, NY.
An Experiment in Flute Headjoint Acoustics
by KATHERINE L. SAENGER
It’s easy! You can make and install a knife-edge for your flute
headjoint using materials and tools usually on hand at home
(estimated time: less than five minutes).
This article originally appeared in the Vol. XXII, No. 1 (fall 1996) issue of The Flutist Quarterly,
the member magazine for the National Flute Association, and is reprinted here with permission.