C# to D#
A more useful indicator of flute pitch?



Collectors and museums use "sounding length" - the distance between the centre of the embouchure hole and the far end of the flute - as an indicator of pitch.  Sounding length is a useful measure for some flutes - particularly Boehm and similar system, as many of the variables are eliminated.  It has big problems however for other flute types:

  • it can't be applied equally to C-foot, B-foot and D-foot flutes
  • it involves the head, whose length can be quite arbitrary when a tuning slide is fitted
  • it can be confused by head shortening, which was not uncommon in the British High Pitch period
  • it actually measures the flute's highest achievable pitch, not the pitch at which the flute plays most in tune.

Because sounding length cannot be relied upon for comparing early flutes, it would be useful to have a more useful and reliable indicator.  To help us identify and evaluate possibilities, let's review the principles such an indicator would have to exemplify.  It:

  • should be applicable to as wide a range of flutes as possible
  • should be easy to measure, not requiring removing keys or special tools
  • should be as definitive as possible

Looking at the options, we can rule some out immediately:

  • anything involving low C or C#, as they do not exist on d-footed flutes
  • anything on the head, as it may have been shortened
  • any of the keys on the body, as they might not exist on a particular flute

What does that leave?

Not much, it has to be admitted.  Probably our best bet is the distance between the centres of hole 1 (C#) and the cup of the D# (Eb) key:

  • every period flute has one of each
  • they are as far apart as we can get if we can't use lower foot and head
  • a trial listing of 8-key flutes against their C# to D# lengths seems to work.


In case you're not familiar with the names of the holes and keys, the white line in the image below indicates the two points between which we take the measurement.  It's actually better (easier and more accurate) to rotate the foot so that the D# key is in line with the finger holes.

Anticipated problems

We know that length alone is not enough to define flute pitch - bore taper, wall thickness and hole sizes are second-order effects that have their influence too.  So we can't really expect a single point indicator to work perfectly over the full range of flutes, eg renaissance, baroque, 8-key conical, 8-key cylindrical, multikey conical and multikey cylindricals.  But if we restrict the range of comparisons to one type, say 8-key conical flutes, we may just get away with it.  We might find that we have to restrict it further to say 8-key English conicals.

In the list below, you'll see a range of flutes I have data for displayed in order of their C# to D# length.  I have separated the flutes into groups of reasonably similar length, and therefore (arguably) reasonably similar pitch.

Notes on the graph above

  • Very Low Pitch Flutes includes flutes from before Nicholson, or harking back to that period.  They are most in tune well below 430Hz; indeed they are probably surviving examples of baroque pitch.  They are very hard to play in tune at A440Hz, but can be retuned if that is considered appropriate.

  • Low pitch flutes include Nicholson Improved style flutes and some later types.  These seem happier in the range around A430, the domestic standard for the period.  They can be played in tune with some care at A440, lower notes tending a bit flat.  They can benefit from retuning if that is thought appropriate.

  • Slightly high pitch flutes are those that seem happiest around the Society of Arts pitch of A445.  This is close enough to A440 to enable them to be played in tune at modern pitch with no difficulty.

  • British High Pitch (452-455) is common in multikey (Boehm, Carte, Radcliff, etc) flutes in the later 19th century, but I do not believe I have yet seen an English 8-key conical flute that works best at this pitch.  Still, we can see what one might measure if we did find one.  Such a flute would be very difficult to play in modern pitch, and would be difficult to retune.

  • Interestingly, however, I have come across a Continental flute clearly made for English High Pitch.  The Mahillon listed above seems to be a perfect example - any shorter and it would reach Eb.

  • English Eb flutes are clearly shorter than D flutes, even those at High Pitch.

  • The Clinton Equisonant No 262 seems out-of-place among the earlier flutes.  This possibly indicates that this big-bore multikey fully-vented design cannot be fairly compared with 8-key instruments without compensating.  We will review this once the flute's best pitch is analysed.

So what does the graph tell us?

Essentially, that if you are thinking of buying a conical 8-key flute to play in modern pitch, you would be aiming at one whose distance from C# to D# is within the range about 245 to 255mm.


The results above are encouraging.  A graph of some of the same flutes using their speaking length was laughably ridiculous.   One flute had a head 15mm shorter than otherwise identical flutes - enough to move it by two whole categories away from where it should be.

Extending the range

There are several ways that the system could be adapted to deal with the full range of flutes equally:

  • Have separate charts for the different types of flutes, eg renaissance, baroque, 8-key conical, 8-key cylindrical, multi-key conical and multi-key cylindricals,

  • Have a conversion table, eg "add 3mm for Boehm bore flutes, subtract 2 for baroque, etc",

  • Involve a more complex measuring system and formula, eg "C# to D# length, less 1/2 the difference in bore diameter at the top and bottom of the body; add 2mm for full venting, etc".

What next?

I'll put the system to use comparing flutes, see where it falls down and see what can be done to improve it.  You might like to try it too and comment on its successes and failings.

Your help invited

I'll be pleased to receive data from owners of old flutes and add them to the list above.  It may help us refine the system and even help identify unmarked flutes by known makers.  I'd like to know:

Make of flute
Model (if any)
Serial No (if any)
Description of flute
Length from C# to D#

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