Flute Tone Investigations "n"
- A Picklist of Potential Investigations

I thought it might be useful to compile a list of issues we may wish to look into, in our quest to understand better the factors that influence the tone we perceive from the flute.

It might take some time to get to all of these, and some of them might fall by the wayside, rendered irrelevant by other findings. And the order they are listed in may not be the order we investigate them in.

The titles are indicative only, and may be replaced by something more appropriate suggested by the content of the investigation.

And there might be a burning issue that has been bothering you.  Let me know, and if it seems potentially profitable (intellectually, not necessarily financially!) and it seems likely we can investigate it, we'll chuck it on the list!

Potential Investigations

1. Of harmonics and levels

In our second article, we saw that, at least in Paul Davis' playing of the Three Maries, the second harmonic was the overwhelming contributor, with the fundamental and higher order harmonics often well below in level.  But how far down does a harmonic have to be before it becomes insignificant?  And does the same level down apply to all harmonics, or are more distant harmonics at the same level more noticeable?

Can we employ simple filtering devices to identify and quantify the perceived contribution of the different harmonics?  Or use harmonic synthesis to explore our perceptions?  Can we relate words like "reedy" to reed instruments? 

2. Development of tools

We'll need to develop our own tools to do these analyses.  In the early days, these will probably take the form of manual data capture and spreadsheet analysers, but, just as RTTA has revolutionised pitch measurement, it would be really good to develop automated real-time tools for tonal analysis. 

Position Vacant: Senior Programmer.  Apply within.  Remuneration package to be negotiated, but limited in form to personal satisfaction.

3. Jet offset exploration

What is jet offset, how do we invoke it, what does it do, how do we perceive it?  Can we associate what it looks like with what it sounds like?

4. Types of flutes

If we have ambitions to be able to detect and measure differences in flute tones, then comparing Boehm, Conical and plain Cylindrical flutes should be easy.  Yeah?  And once we've done that, the next step is investigating the difference between big-bore Pratten's, medium bore Rudalls and small bore GLPs.  And if we can do that ....

5. Types of Players

While Gregor in the paper referred to in the Introduction to this series clearly showed the different metals produced no differences, he also proved that different players make all the difference.  His players were probably pretty much "out of the conservatoire mould" by comparison to the range of playing backgrounds our community comprises.  Can we characterise players in this community in any meaningful way, or is it a complete spectrum or jumble?  Are some sorts of players predisposed to certain kinds of flutes? Are there some tones that we all admire, and others on which we are divided?   Can you move along the spectrum if you want to?  Can our tools help you move?

6. Technical resources

What equipment and software are being used in these investigations?  What are their limitations, and are these impacting on the quality of the measurements?  Do they impact on the findings?  How good enough is near enough?

7. Crunch the numbers

Once we settle on some measurement philosophies that seem to have the capacity to bear fruit, we have to settle on some number crunching protocols.  These need to be able to stand up to examination, and others might like to see if they can replicate the results.  Knock yourself out!

8. Further Reading

A lot has been said and done in this field over the years, admittedly almost all in terms of other kinds of flutes.  When is it applicable and when is it not applicable to our kind of flutes?  A lot of what is available is on the web.  Links and maybe comments.

9. Effects of embouchure cuts and chimney depth

Different embouchure cuts and chimney depth produce audibly different flute tones.  If we can hear it, hopefully we'll be able to see it, and understand why.

10. At the Foot of the Matter

Early flutes had Short D feet, 19th century flutes had C feet, and modern Irish flute have a choice of Short D, Long D and C feet.  Can we detect a difference in sound level or quality?  Are there gains and losses?

11. Stopper position and tone

Elsewhere on this site, we've examined the effect of stopper position on tuning.  But what it its effect on tone?  Can our tools tell us?

12. Effects of materials

We saw in the introduction that the significance of various metals in metal flute construction has been disproved, by both listening trials and in careful measurement.  But our materials are not so limited in range - is it possible that they still do have an effect?  Can we tell the difference between a blackwood and a pine Prattens made with the same measurements and tools?  Can we go on from there to determine which of the possible characteristics are responsible for what tonal differences? Does this then suggest what materials will be better than others, or does it come down to a balance in taste?  Can we detect metal head liners, full and partial, and metal lip plates?  Does oiling polymer make any sense?  Do ebony and blackwood differ in tone?

13. What's best?  Easy, or Manageable Pain?

It's often put forward that an easy-blowing flute may not be capable of as good a tone as some more difficult-to-play instruments.  Can we find anything to support this view?  Can a flute be too difficult to play?  Or too easy? 

14. Only flat for Wusses

First half 19th century flutes tended to have low notes that tended flat.  Players learned to accommodate this.  How did they do this, and how did it work?  Modern flutes don't have to replicate the flat-footed feature, but some do.  Some players can't handle it, others can't seem to live without it.  Is this just laziness on the part of the maker, coupled with hairy-chest syndrome on the part of the player, or can we detect real advantages in this approach?  If so, can we give guidance to those who would like to play that way, but so far can't?

15. The Dark Side, Luke

What contributes to "darkness" in Irish flute playing?  Can we measure darkness?  Can we learn darkness?  Can we control the dark side?  What proportion of darkness lies in the flute and what proportion in the player?  Is Cut-off Frequency implicated?

16. Spectrum or Cepstrum?

A Cepstrum is a single spectrum which attempts to replace a family of spectra.  (Cepstrum, pronounced with a hard C, is a manufactured word - spectrum with the first four letters reversed.)  We've seen that the spectra of different notes varies significantly, but is it possible that we could still use a Cepstrum to describe a flute?  It would be handy, but would it be too misleading? Can several cepstra adequately define a flute (eg low notes, LH, 2nd octave)?

17. Signal to Noise Ratio, or Clarity

You've probably encountered flutes that are magnificently clear, and others that are wallowing in noise.  Can we develop a tool to measure signal-to-noise ratio like the HiFi people do?  But is it that simple?  Is there good noise and bad noise, and if so, what's the difference?  Can our tool learn the difference?  Can we identify the noise sources?

18. Dynamic vs steady state

It's often been noted that our ability to recognise the tone of an instrument (eg differentiate between a clarinet and a violin) is much reduced if the starting transient is taken off or disguised.  How does the starting transient of our flute affect our perception of its tone quality?  What defines and characterises a starting transient in a music that largely employs finger articulation?

19. Undercutting

Can we detect the effects of undercutting on tone?  Just how sharp would our measuring tools have to be?

20. Low whistle?

Can we identify the differences in tone between the D flute and low D whistle?  (Heh heh, if not, you'd have to ask are we getting anywhere!)

21. Projection - urban myth or exploitable reality?

It's often argued that some flutes sound no louder up close but "project better".  Can we find any evidence to support the claim? 

How different in spectral content, amplitude and phase are the tones leaving the embouchure and other end of the flute?  How far back do we have to be to hear them combined?  I.E., where does the near-field end and the free-field begin?  Do some flutes or playing styles take better advantage of the ear's most sensitive frequency bands?  Does the flute carry better than some other instruments simply because it is louder? Does the player seeking projection above a mix of other instruments have to tailor their tone to avoid being masked by the particular mix of instruments - ie do they need to find some unclaimed spectral space?  Do they do this naturally or consciously?

22. Flute add-ons - snakeoil or what?

Fluteplayers, even the best of us, are never happy with our tone.  This makes us easy marks in terms of scam add-on products and treatments.  Which is not to say that all add-on products or treatments are scams.  So, clearly we need to be able to tell between them.  If we can develop tone measurement tools good enough to investigate the issues above, they should also be able to confirm changes brought by the add-ons.

23. New heads on old flutes

It's my routine experience that a 19th century flute usually benefits dramatically from being fitted with a new head.  I'd feel better about that, if I could always confidently point to what's wrong with the old head.  Sometimes it's obvious, and that's fine.  But I've had many cases of old heads that just don't sound good.  I've tested them for leakage, replaced stoppers, inspected them for damage to the edge or chimney and found nothing.  Clearly I need to look harder!

24. Instabilities

We've probably all come across examples of instabilities in flutes.  Cover the embouchure too much or blow too hard, and some notes start to go wobbly - that kind of thing.  What's actually happening here?  Are there more than one type of instability?

25. Musicality

What contributes to a feeling of musicality in a flute? What detracts from it?  Do we take into account tone, tuning, responsiveness, clarity, articulation? Others? Do mechanical matters (easy and operation of keys, firmness of tenons) impact on such feelings (ie are distractions problematic for our perception of the whole?)

26. Responsiveness

What is responsiveness? What contributes to it in a flute? Is it just efficiency (the amount of sound produced divided by the amount of air flow)? Or do matters like articulation contribute to our perception? How sensitive are we to differences in adjacent notes. What aspects of adjacent notes impact on this - tuning, volume, tone,

27. The Effects of Aging

Does a new flute really improve with age, or is it just that we get better at blowing it. Or both? If a maker were to take a well blown-in flute and return the bore to original state, would the blowing-in process be reversed, the clock reset? Can we detect "falling asleep" - the oft-reported feeling that old flutes need reawakening. What changes during re-awakeing? Moisture content? Efficiency? Tone?  Tuning?

28. Boundary layer vs blowing in

It's argued by acousticians that a boundary layer exists at the walls of a woodwind, separating the free flowing air in the middle from the air that is in contact with the walls.  Consequently, a little roughness of the walls shouldn't matter.  The boundary layer is usually deemed to be about 0.1mm thick.  If so, it seems that this concept is in some disagreement with the notion that a flute can be "blown in" - surely the boundary layer will insulate the air from any changes to the wall material or surface.  Can these concepts co-exist peaceably?

29. Blowing in - blowing out?

There is a view that clarinets and oboes have a finite lifetime - that they will "blow out".  It's hard to see any major difference between the clarinet and the flute, yet vintage flute players don't seem to make the same observation.  What's the story?  Is it possible that what the reed players call "blowing out" is the physical deformation of the bore we call strangulation?  If so, we are familiar with it.

30. Harmonic Dynamics

Is it enough, for the purposes of investigating flute tone, to take a note at a time, or do we need to dissect that note further to see the full picture? For example, does the final blend of harmonics build up together at the start of the note, or do some develop later than others? Can we hear the difference? Do players vary their harmonic mix during a note, and is it conscious or unconscious? Is it something that they only have time for in slow pieces? Is it a significant factor in the player's unique sound signature? What tools are useful in determining and visualising this?

31. Dynamic vs steady state

It's often been noted that our ability to recognise the tone of an instrument (eg differentiate between a clarinet and a violin) is much reduced if the starting transient is taken off or disguised. How does the starting transient of our flute affect our perception of its tone quality? What defines and characterises a starting transient in a music that largely employs finger articulation?

32. Perception thresholds

A player is a lot closer to the flute than the average audience member, but not much closer than another player in the next seat. Can we detect a difference in perception thresholds between all three? Are any differences adequately explained by drop in volume level with increasing distance? Does amplification (or recording and replay) to realistic levels restore the ability to perceive fine detail? Or is the increasing proportion of reflected to direct sound responsible for blurring fine detail? Is a small amount of blurring a good or a bad thing? (Analogous to soft focus in portrait photography?)

33. Vibration

Flute players often comment on the excitement of feeling the flute vibrating under their fingertips. But is it the flute vibrating, or the air column? If it's the flute, isn't that a bad thing - the pliable walls of the container sucking energy out of the vibrating air column inside, and dissipating it as useless heat? If it's the air column, why do some flutes seem to do it more than others? Efficiency of the flute? Size of the fingerholes? Other? What other information passes back from the flute to its player?

34. Resistance

Players talk about the resistance offered by the flute. It can be too high (the flute is stuffy), or too low (feels like blowing into a vacuum). Can we actually detect "back pressure" at the embouchure? Is that what we call "resistance"? Or are we assessing audible responses, eg the ratio between the effort we put in and the amount of sound that comes out, or tone-related changes?

35. Edgy, but not nice

Sharp edges in the wrong places can generate a nasty edgy noise.  I suspect it's something like scrape modulation noise in an analog tape recorder.  Can we detect it by measurement?  Can we set an acceptable maximum level for this sort of noise?  Can we devise a test that helps us find the location of the problem?  What remedies are the most effective?  Would a "wind-tunnel" approach (in our case, passing large volumes of air through the flute) enable us to exaggerate any effects and make problems easier to detect and deal with?

36. The effects of key holes

Some have argued that the performance of a keyless version of a 19th century flute will suffer unless the volume of the holes under the pads has been factored into the bore.  My perception is that there is actually a gain because any acoustic losses are more than overcome by fewer aerodynamic issues.  Are either of us right, or both of us wrong?

37. Just how precise?

Does a flute maker need to work to 0.01mm precision, as has been claimed?  What is the first indicator of insufficiently accurate work - tuning, tone, response, a combination, other?  Which parts of the flute are most demanding of precision?  Which are least?  In the light of findings, how do we interpret Ward's and Rockstro's very opposed comments on chambering?  What could chambering mean, and can we find evidence of it?

38. Vowels

Can the flute player emulate vowels in singing?  Is that something we do when approaching airs?  Is it conscious or subconscious?  How would vowels present in terms of harmonic structure?  Does "hearing the words in our head" change the sounds we make?  Does it assist listeners to appreciate the air?

39. Just blow in the end, OK?

It's bothered me for a long time that whistle players such as Mary Bergin and the late Mico Russell could produce tones from the common Generation whistle that were radically more attractive than the tones I could produce.  What's going on there?  On the face of it, the scope for manipulating tone on a whistle is not great.

40. It's all in the way you hold your mouth...

Like the one above, it's sometimes claimed that you can alter the tone of the flute by the way you hold your mouth, throat, vocal chords etc.  A very interesting one because it's hard to see much scope for interaction across the jet (the pushing string uphill problem). But it should be possible to test for it by adding a variable volume artificial mouth at the back of the artificial lips in an artificial flute blower. And perhaps a microphone in the mouth?

41.  Genetically predisposed to flute

I often use that expression to cover those people who seem to be able to get luscious tone on day 1, can play the most difficult tunes effortlessly, and can play flutes that the rest of us would send for repair without seeming to notice a problem.  Can one be genetically predisposed to flute, or have they just put in the hard yards and are now reaping the benefit?  Can we discern any physical (or mental) features that could be part of their predisposition?

n.  Other things we'd like to know

I keep thinking of other things we would like to know about the flute and flute playing, that nobody seems to have worked out, or at least written down somewhere where we can find it.  So, I thought I'd record them here so they don't get away, until I can figure out a better place to keep such a list!  Feel free to add to it!

  • Which fabric swabs water the best?

  • Which oil slows the intake of water the most?

  • How quickly does a flute take on water when played

  • How much air do we pump through a flute per hour

  • What impact on our cardio-vascular system does energetic flute playing have?

  • What is the distribution of temperature along a flute?

  • What is the rate of rise of temperature in a flute as we start to play?

  • When does the temperature reach equilibrium?

  • Does the intonation (tuning) of an old flute change as it is blown back in?

  • Can a bad or weak player cause a flute to misbehave, and a good player cause it to come back into line?   (The subject of an old claim.)  If these changes are detectable, are they in the form of pitch or performance changes?


Whoa, that should be enough to go on with for the moment!  And we've strayed somewhat from the central issue of flute tone, but that's OK, they're still good questions we'd like definitive answers to.  I'll get to them as time permits, and as I build up and test my resources.  Keep in touch!


Thanks to all those who are following this series and providing suggestions and comments!


The Flute Tone Investigation Series so far:

or Back to McGee-flutes Index page...


  Created 2 Nov 09