I have twice heard people whom I respect question whether playing very high notes can damage a recorder. I assume they are right, but the mechanism for the damage is not obvious, and therefore the degree of damage and the means of preventing or curing it are not obvious either.
To begin with a clarification: very high notes means notes beyond the normal range of a recorder, which is two octaves and a fifth – the range used by Baroque composers. In practice, though, this should be extended by a tone; the next two semitones are very similar in quality and play to the notes immediately below. So I shall take “very high notes” to mean notes above the third-octave A for C instruments, and above third-octave D for F instruments.
Very high notes have been in use for nearly a century. The great recorder virtuoso Franz Bruggen back in the 1960’s was playing a full three octaves on his recorders, and composers from that period were employing these notes: for example, Louis Andreissen in his well-known “Sweet for Recorders” uses a fourth-octave F# on one occasion. Further, the tutor “Recorder Technique” by Anthony Rowland-Jones, whose first edition was published in the 1950’s, gives a fingering for a fourth-octave G (on an F-bass recorder).
I have no evidence that playing or attempting to play these high notes has actually caused damage – but that is not proof; it is possible that the high notes did not cause direct damage, but potentiated damage from other sources, or else caused damage that was too long-term to attribute.
Enough background – how could very high notes cause damage? These notes are distinguishable from the notes immediately below by three characteristics: pitch is higher, breath pressure is much higher, breath speed is much higher.
Pitch surely is irrelevant here. Very high notes on one instrument are simply ordinary notes on an instrument an octave higher, and there is no evidence of descant and sopranino recorders crumbling in their owners’ hands.
So we need to consider breath pressure and breath speed.
Now we can make another simplification. The breath pressures and speeds in a recorder even for very high notes are by no means unusual in other wind instruments, and there is no question of damage to those. Therefore, those aspects of the recorder that are shared with other wind instruments can be eliminated. There is no danger of splitting the wood, of popping the joints, of disrupting keys – indeed, we can disregard the whole of the middle and foot joints. If very high notes cause damage, it must be to the head joint, and in particular to the mouthpiece.
So now we can focus on the three parts of the mouthpiece: the windway, the window, the edge.
Here we have a new tool at hand: the Bernouilli Effect. This is the – slightly strange – fact that when a fluid (liquid or gas) is moving, the pressure across the flow drops. So when we blow through the windway, the pressure on the walls of the windway should be small – indeed, it may even be a suction! This implies that the very high notes can not be damaging the windway; indeed, almost the opposite. Similarly the window – despite the four or more internal corners where potentially a crack could start – the window will not be damaged by the fast stream of breath.
That leaves the edge.
The edge is hit by the breath, and therefore the Bernouilli Effect doesn’t apply. The edge gets the full pressure of the breath directly on it. Is that pressure, in that volume, at that speed, enough to damage the edge? I no longer have the means to do the sums, but I don’t believe it. The edge is not paper-thin; it is wedge shaped. The angle of the wedge is different from instrument to instrument, but I have many times seen players blow sharply into the window to clear dust or condensation, without the slightest sense that they are taking a risk – and that is blowing onto the side of the wedge, which is far more likely to damage it or to damage the window. So no, the air itself is not sufficient to damage the edge.
There is another point to consider, and that is what the breath is. The breath is not pure air: it is indeed mostly air, but it is air that has just emerged from a very wet pair of lungs, lungs which are usually warmer than the outside world. The breath is therefore at best supersaturated with water, but in the level of pressure of the very high notes, it will be turbulent; almost certainly it will have begun to condense out.
In other words, it’s not just a jet of air; it’s a jet of air with huge numbers of droplets of water in it. Those droplets will not be visible – they will be nanometres in diameter at biggest – but they will be there. And as the breath changes direction at the edge, where the flow is turbulent, centrifugal force will make them hit the wood of the edge; wood that contains many pores, tiny in themselves, but each far bigger than the droplets, so many of the droplets will penetrate deep into the wood.
Is that a good thing? No. The wood becomes wet relatively deeply in; the whole outer surface of the wood will therefore swell – a tiny amount, yes, but still there, and much deeper that would be expected. Furthermore, because the notes are part of a whole piece being played, there will be no opportunity for the wood to dry before the next note hits – even if that note is not very high, its humidity will suffice to protect the dampness deep in the wood. As the wood eventually dries, it will not quite return to its original form; again the change will be nanometres or even picometres on each occasion, but enough for internal strains to build up over time.
In the end, and depending on the type of wood, the direction of the grain, the angle of the wedge, the radius of the tip of the wedge, it is possible that the surface of the tip of the wedge may craze, or that microcracks could develop from the tip of the wedge inwards. In either case, the effect is likely to be too small to see with the naked eye, but the roughening of the surface of the wedge will cause a deterioration in the tone of all the notes, not just the very high ones.
And we can not exclude the possibility of a visible crack eventually developing.
It is obvious that this is largely hypothetical; whether the mechanism is real, and if it is real how long any damage would take to matter, these are unquantifiable on what data I have. But it is a possible mechanism for damage from very high notes, and it therefore justifies the instincts of the people who question whether playing very high notes could damage a recorder.
The answer to the question is that we don’t know, but it might; there is a way that the damage could happen.