 The Clarinet BBoard
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Author: Ben
Date: 2004-03-22 21:05
For getting balanced spring tensions on the keys of a bass clarinet, is it possible to make them light and even enough that it will feel similar to well adjusted Bb/A clarinet? Or, do many keys have to be a bit stronger than a smaller clarinet, requiring one to just have to get used to a different feel (and stronger fingers!)?
I know one needs to have a spring strong enough that the key wont bounce, or blow open, so are there any particular keys which may be most prone to this, on a bass, if too light?
Right now on the bass I have, the keys are still a lot stiffer than my Bb/A clarinets, making my technique a lot more sluggish and clumsy! For instance, playing from throat A to middle B (over the break) is a lot harder; particularly when ascending.
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Author: David Spiegelthal ★2017
Date: 2004-03-22 22:39
Bass clarinet spring tensions really do need to be heavier than those on a Bb clarinet, because the keys have considerably more mass, and the pads have more surface area on which to seal. The biggest problem notes are the low Ab/clarion Eb which tends to blow open if there exists even moderate resistance in the reed/mouthpiece/instrument system, unless the spring tension is set fairly high (which can be hard to do sometimes because of the short length of the spring and difficulty in accessing it on some instruments). Also, the throat A on bass clarinets having double-automatic register vent mechanisms can be stiff, not because of any particular single spring tension but because of the combination of levers and linkages (usually involving multiple springs) it has to operate.
Rather than set lightness of spring tensions as a goal with bass clarinets, my preference is to get them fairly heavy, but even and consistent --- this is achievable and precludes problems with pads blowing open or not sealing properly. And the player will get used to it.....
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Author: cujo
Date: 2004-03-23 04:45
You do not really need springs stiffer on a bass. As long as the keys do not blow open while playing loudly the tensions do not need to be overly stiff.
Keys normally open could/should have the lightest as tension possible as long as key still moves quickly.
...
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Author: Gordon (NZ)
Date: 2004-03-23 10:10
Yes! Just as David said.
First, there is a lot of heavy vibration in the air in a bass clarinet, with high amplitude. This can push lightly sprung pads open. Same in sax. This effect is made much more significant because of higher diameter tone holes, resulting in the air pressure producing a greater force.
Second, you may think that for a normally open spring, the tension needs to be only slightly more than what is required to lift the key, and that this extra would be the same as for a soprano clarinet. However, the keys have far more inertia, so there is the issue of needing sufficiently extra forces to raise the key sufficiently quickly. F = ma. Higher mass means more force needed for the same acceleration as it rises.
Third, on a bass clarinet there are many more mechanical linkages. Usually when there is a linkage, the finger has to press against at least two springs. Also, there is often significant friction at the linkage.
Fourth. larger keys may mean a different leverage set-up, with the key cup further form the hinge, but the 'touch piece' not necessarily further from the hinge than what it was on a soprano clarinet. This may necessitate a stronger spring to exert enough force at a closed pad, and a stronger finger force to oppose it.
.... etc, etc.
In short, it is a completely different mechanical set-up. An astute technician can make the 'feel' as good as possible, but it can never feel like a soprano clarinet.
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Author: graham
Date: 2004-03-23 11:46
I cannot see why the manufacturers have failed to develop technological solutions to this problem.
How about power assisted keys, feather light to the finger's touch, with vice like clamping power at the pad end. All you do (surely) is fit a turbo/generator type of device at the neck part of the instrument. This generates power that can be transfered to powerful electromagnetic key shutting systems. When you blow, you create the power assistance. The only problem I see is that the quieter the passage, the heavier the keys will be, whilst the louder the passage, the lighter they will be, but perhaps this can be evened out by fitting a buffer such as a capacitor to smooth any generation and use.
Or perhaps the leverage could be increased mechnically by introducing tiny pully systems on the offending keys, thus generating extra leverage within very small spaces.
I am sure DS would find these prototypes an absorbing project once he has finished his C extension joint. Could change the whole history of bass clarinets.
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Author: Tim P
Date: 2004-03-23 13:32
How about air actuated cylinders. Air pressure/volume could be stored in a bag similar to the bag pipes and Normally open or Normally closed rams/valves could be triggered by any sort of configurations. Maybe even computer generated. The clarinet would be held by a stand similar to a Microphone stand. the "artist" would step up to the device, place his/her mouth on the mouth piece and blow. The computer would take it from there. A small pick up microphone at each tone hole would feed back into the computer which then could adjust the height of the valves to change pitch slightly. We could even sub contract "Acme Rubber Doll" to make an artificial embrochure that could be varied and controlled by the feed back.
The "artist" would still have to spit on the reed occassionlly to keep it moist and just so we don't lose that human touch we allow him/her to adjust the volume.
The Tempo Adjustment knob would be on the conductors stand. (but of course, in keeping with tradition, it would NOT be functional)
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Author: David Spiegelthal ★2017
Date: 2004-03-23 15:17
Graham and Tim,
I assume your suggestions were tongue-in-check, but I'll respond anyway: the 'technological solutions" (to what I consider to be non-problems) would have to follow the laws of physics --- which include the parameters Gordon and I mentioned, namely mass, inertia, and lever arms. The proposed solutions of electric solenoids, hydraulic cylinders, etc. are, bluntly put, BAD IDEAS --- I hate the feel of the (inevitably over-boosted) power steering on my car, I dislike the spongy feel of power-assisted brakes, and I'll be damned if I want any device on my musical instrument that gets between my fingers and the key cups, or requires any power to operate other than my finger muscles! Sorry, but there's a place for 'modern technology', and there's a place for traditional, well-tested simple devices.
End of sermon.
Dave the Luddite
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Author: Tim P
Date: 2004-03-23 16:05
TIC TIC TIC
I wonder if way back in the dark ages when the 1st guy put a 1st lever and a valve(pad) on the hollow stick with holes in, he was thought of as a some sort of crazy guy with no feeling for his music. ya know if ya can't feel the vibration under ya finger tips, How ya going feel the music.
TIC TIC TIC
I suppose that one of the laws of physics that has to be considered is how the force of the air on the pad is increased expontially as the area of the pad is increased. I believe this to be a function of Square which adds up very quickly.
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Author: David Spiegelthal ★2017
Date: 2004-03-23 16:40
Assuming that proper pad sealing requires a certain value of pressure on the rim of the tonehole, and with Pressure = Force x Area, and with Area increasing linearly with Diameter (A = pi x D), then the Force required to seal a larger bass clarinet pad would increase linearly with Diameter ---- not exponentially.
Tim -- add technology if you like. Personally, I still miss my old Alfas and Fiats with non-power steering, the best-steering and most-fun cars I ever owned. And nobody is going to put "power keys" on my horns, that's for sure.
p.s. My bass clarinet low-C extension was completed about a month ago and is in regular operation --- has survived an orchestra concert and a wind ensemble concert without any problems. And no solenoids, hydraulic cylinders, or nuclear reactors are used to operate the keys -- just my left thumb.
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Author: Tim P
Date: 2004-03-23 17:32
force = pressure x area. look at the units
#/in2 X in 2 = #'s pounds is force
pressure equals force divided by area. as pounds PER square inch
Do you have to adjust the timing in your fiats or does it advance automatically as you drive. Also I hate those new fangled steering devices called Rack and pinion. it was the ruination of driving it only led to the other evil called power steering. I hope your cars don't have rack and pinion.
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Author: David Spiegelthal ★2017
Date: 2004-03-23 21:07
Of course it was tongue in czech --- I knew that --- I just decided to take the opportunity to make a semi-serious point, that the latest is not necessarily the greatest (and may well be worse than the previous). I can't believe I screwed up the force-pressure-area relationship (gee, I only have a master's degree in mechanical engineering) --- this is what happens when we type too fast and don't read what we've just written before posting. As for my past cars:
1974, 1978 Fiat 124 Spiders: It's been a while -- I believe they had worm & sector steering
1986 Bertone (formerly Fiat) X1/9: Rack & pinion
1978 Alfa Spyder Veloce: Worm & sector
1979 Alfetta GT Coupe and Alfetta Sedan: Rack & pinion
I really like rack & pinion --- it's the power assist I can't stand. Even the BMWs I've had, with their vaunted steering precision, couldn't come close to the tactile feedback I got from my non-boosted Italian car steering.
All my cars had automatic ignition advance, although my 1968 VW Squareback had been retrofitted with the infamous Bosch "Blue Coil" which had mechanical (centrifugal) advance only, no vacuum advance.
That should bring you up to date..............Sorry to all for the major digression from topic.
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Author: thomas.b
Date: 2004-03-23 21:07
Gordon's answer is perfect and David illustrated it with a nice formula. You can even feel the differene between a German Bass clarinet and a Boehm Bass clarinet. The German Bass clarinet has a smaller bore and somewhat smaller pads. Therefore the spring tension is somewhat smaller than in Boehm Bass clarinets (my Bass Clarinet: Buffet 1193-2). But to be honest: I never cared about the spring tension of the instrument, I was glad that the mechanics worked without problems, I had never (1/2 year) to adjust anything, so that I can concentrate on enjoying the wonderful feeling of playing a bass clarinet .
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Author: Mark Charette
Date: 2004-03-23 21:21
David Spiegelthal wrote:
> 1974, 1978 Fiat 124 Spiders: It's been a while -- I believe
> they had worm & sector steering
1974 124 coupes had worm & roller steering w/ adjustable backlash. I had 2 of them simultaneously in 1978-1980- one to drive and one for parts ... but sometimes we couldn't figure out which was for what ...
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Author: Tim P
Date: 2004-03-23 21:39
yes of course.. point made.
however, my point that i tried to make in an off hand way was..
technology will keep making improvements and everthing that we use, not matter how"old fashion" is the result of some technological change.
only the real improvements will last. but the clarinet that we play today has had many improvements and I believe there will be more.
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Author: Gordon (NZ)
Date: 2004-03-23 22:27
Now for a much more realistic improvement, as I have mentioned before:
A new alloy:
- It is several times stronger than current key metal, and considerably lower density, so keys can be made a fraction of the weight.
- Seems to be very rigid, resulting in less twist for those long keys?
- It can be cast at low temperature, almost as easily and cheaply as plastic, so no arduous soldering to make keys.
- It comes out of a mould so accurate that cast razor blades do not need sharpening.
Yes it does exist. Used for a cell phone case. Used for cell phone hinges. used for golf clubs - I think they have been banned from some tournaments because they are so good. Used for scalpels for eye surgery. Used for tennis rackets with a much larger 'sweet spot'.
It's called "liquidmetal" (trade mark) - because it has no crystalline structure as other alloys do. WAtch this space! which will be the first manufacturer to use this for musical instruments? One in China? :-)
http://www.liquidmetal.com/
Check out the video of the bouncing balls! Extraordinary!! Perhaps this also translates into special acoustic properties for mouthpieces.
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Author: Gordon (NZ)
Date: 2004-03-23 22:34
With regard to all the far-fetched posts above....
Many of the problems we have with instrument originate from pads not lifting vertically, but hinging from the side.
Perhaps a not so far fetched development would be for key cups to be mounted on a pair of sleeves that slide vertically from the tone holes. Indeed, these mountings could be hydraulic cylinders, with hydraulic linkages to other keys. That should satisfy David, because the action would be so positive. A degree of appropriate amplification or otherwise of force/travel could be engineered into by selection of appropriate piston sizes.
The equipment seems to be already there. I note one specialist supplier of micro-hydraulics with components down to 0.01" diameter"
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Author: David Spiegelthal ★2017
Date: 2004-03-23 23:11
Gordon,
The vertical-sleeve mounting you describe (a la Morgan automobile sliding-pillar front suspension? has a potentially fatal flaw --- any cocking of either cylinder causing binding of the sleeves. You'll recognize this phenomenon from any number of everyday objects that are mounted that way. Another idea I've considered is a parallelogram mounting of the key cup, with two parallel arms --- but it would be subject to wobbling if there was any play in any of the four pin joints. As for hydraulics --- they tend to leak, unless very expensively made -- but it could work. This liquid metal you describe --- sounds an awful lot like cast magnesium to me....
Mark, thanks for correcting me on the Fiat steering, you're absolutely right. I wasn't sure about the sector part (such boxes also have screw-adjustable backlash, like recirculating-ball boxes).
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Author: Gordon (NZ)
Date: 2004-03-24 10:24
"Liquidmetal alloy is a unique blend of titanium, zirconium, nickel, copper and beryllium"
No magnesium.
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Author: David Spiegelthal ★2017
Date: 2004-03-24 14:07
Mmmm....liquid metal sounds delicious............I'd like to pour some on my breakfast cereal...............Sure like to find out how those wild 'n' crazy chemists and metallurgists manage to (a) make a homogenous mixture out of all those dissimilar metals, and (b) get it to cool to room temperature without the formation of any grain structure.
Sounds like the 'cold fusion' thing all over again.
Dave the Skeptic
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Author: graham
Date: 2004-03-24 14:36
This is a Fiat driver's approach to things. As a life long Citroen driver, I have a different perspective.
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Author: saxlite
Date: 2004-03-24 14:42
David S--check your math--the area of a circle is pi x (r squared)
or pi x (D squared) / 4. So it goes up exponentially, not linearly with increasing pad size. Just to be accurate, sorry. Carry on......( Gordon, how could you have missed this....?)
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Author: David Spiegelthal ★2017
Date: 2004-03-24 16:44
On third thought (or in my case, probably first thought), it's not quite so simple ---- consider this:
The wind pressure on a pad does indeed cause the force on the pad (as saxlite pointed out) to increase with the square of the pad diameter (exponentially increase, in other words, with an exponent of 2.0). However, since the pad basically seals only along its perimeter over a finite thickness of tonehole lip, the sealing area is approximately equal to the perimeter length (which goes as pi x diameter) times a very small thickness (the lip of the tonehole) --- so the sealing area on which the key force acts (generated by finger or by return spring) increases only linearly with an increase in pad diameter. To keep the pad closed, the sealing force on the tonehole rim must equal or exceed the force exerted by the wind pressure inside:
[(Spring or finger force) x (key linkage lever arm multiplier)] > [(Wind pressure) x (1/4 x pi x diameter-squared)],
where
the term in brackets on the left is also equal to: [(pad pressure) x (diameter) x (tonehole rim thickness, a constant)].
Assuming that pad pressure has to stay within a given narrow range (too little compression = bad seal, too much compression = damage or shortening of pad life), then let's call (pad pressure) a constant, for the sake of argument. Then the left-hand side of the equation would increase approximately linearly with diameter, whereas the right side increases as the square of the diameter (for a constant wind pressure).
If you're still with me (and if my math is better this time), then it means that, for a given internal wind pressure, as pad diameter grows, eventually either the pad won't seal, or the required pad pressure will tear or crush the pad. The saving grace, I think, is that as an instrument grows in size, the internal wind pressure (overpressure) decreases --- so the 'constant wind pressure' assumption is not valid.
End of class, please turn in your homework assignments tomorrow....
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Author: thomas.b
Date: 2004-03-24 20:58
I think, this is wrong. The pad seals only along the rim, but the sealing condition is not your rim argument, but only that the force the pressure executes on the whole pad (area) is smaller then the force, the spring executes (via the key) on the pad. otherwise the pad will elevate and the rim can not seal.
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Author: David Spiegelthal ★2017
Date: 2004-03-24 21:28
thomas,
I think you and I are actually saying the same thing. My point was that the force that the spring (via the key) is ALLOWED to exert on the pad is limited within a fairly narrow range by the minimum and maximum allowable compression of the pad on the tonehole rim --- so there are practical limits to how light and how heavy we can set the spring tensions.
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Author: Gordon (NZ)
Date: 2004-03-24 23:34
It is interesting that if you do a blow pressure test on an instrument body, and gradually increase the air pressure, the first pad to lift and audibly leak is the one that already had a tiny leak. This seems to be a phenomenon rather independent of the tone hole diameter or spring tension. The presence of a small area around the sealing circle which does not seal well, allows the pair to get in under the sealing circle and lift the entire pad.
I did not read all of David's last post, but I am quite sure there are other factors involved which override the pi x r squared thing, as he suggests.
I did miss it though. I often peruse this site around 4 am before going to bed.
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Author: Tim P
Date: 2004-03-25 12:11
Dave
I am still confused
you say..
"The saving grace, I think, is that as an instrument grows in size, the internal wind pressure (overpressure) decreases --- so the 'constant wind pressure' assumption is not valid."
you say that as the instrument increases in size, I guess you are saying that the bottom of the lower joint starts to increase in diameter so the pressure drops.??????
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Author: saxlite
Date: 2004-03-25 13:12
Tim P: yes, the pressure decreases as the cross-sectional area increases. Ultimately, the pressure at the open tone hole must be equal to the ambient (room) air pressure. This is true, even for a constant cross section tube such as a clarinet or flute. (This is a simplification; there can be various nodes and anti-nodes, but is sufficient to understand the situation under discussion.....)
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Author: David Spiegelthal ★2017
Date: 2004-03-25 14:31
Since the average overpressure (pressure above ambient) is created by the player blowing air into the instrument, and the instrument has a certain impedance (mechanical and acoustical) which prevents the pressure from immediately equalizing with atmosphere through the open toneholes and open end, then in general, given that a person can only pump a finite flowrate of air into the horn (within a fairly narrow range), then the overpressure will generally decrease as the instrument gets larger -- like pumping up a tire: the larger the tire, the less the pressure increase for a given number of strokes of the pump. Another half-baked analogy for your dining and dancing pleasure.......
Where's Dr. Benade when we need him??
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Author: Tim P
Date: 2004-03-25 14:38
Dave
I am still confused
you say that as the instrument increases in size, then the internal pressure decreases. I assume that the point is that the bottom of the lower joint starts to increase in diameter so the pressure drops.
If this is indeed what you suggest then I am very confused. Seems that as the diameter increases then the velocity decreases. (Q in = Q out and Q = Area x velocity)if the velocity decreases then the pressure has to go up.
the opposite is true, too. This is why the Ventura tube in the carborator of your "old tecnology" cars works?? the ventura is so small a Negative pressure is obtained.
wouldn't this same principle of "conservation of energy" apply inside the bore of the clarinet
the tire analogy should only apply to static conditions and volume.
Tim P
not an engineer. just a lowly engineering technologist.
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Author: David Spiegelthal ★2017
Date: 2004-03-25 14:58
Tim,
I said that, as the instrument increases in size, the AVERAGE amount of OVERPRESSURE (dynamic pressure increase above atmospheric) decreases because a human player can only pump a fairly constant flowrate of air into the horn. Has nothing to do with taper of the horn, velocity, etc.
The tube in a carburetor is a "venturi" -- Ventura is a place in California. In a venturi, at the narrowest part (throat) the AVERAGE velocity must increase to maintain conservation of mass, and consequently the AVERAGE pressure must drop to satisfy Bernoulli's law --- but this is irrelevant to our discussion. The case we're talking about is what I would call "quasi-static" -- because the flowrates and velocities are low, and the mechanical/acoustical impedance of the instrument is relatively high, and basically we're talking about creating STANDING waves in the instrument, as opposed to a steady air flow situation such as in a carburetor. That's all I'm going to say about this, as I'm already out of my depth and liable to get into more hot water! If you want the real scoop, read Arthur Benade's book (NOT the O. Lee Gibson pamphlet, please!).
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Author: Don Poulsen
Date: 2004-03-25 15:06
Two points of correction:
(1) "Exponentially" is the incorrect term for the relationship between force and pad diameter. "Geometrically" is the correct term. ("Exponentially" implies a relationship proportional to e^ax.)
(2) The air pressure within the instrument is insignificant with regard to raising and lowering pads/keys. (To illustrate, consider the point of highest air pressure -- at your mouth. Create your embouchure without the instrument and blow like you would into the instrument at a forte or fortisimmo level. Stick your finger in front of your mouth and wiggle it up and down as if your mouth was the tone hole. The air stream doesn't create significant resistance does it?) The only things relevant to the lifting of the keys are, as discussed above, the inertial and friction of the keys and how fast you want the key to move out of the way when you lift your finger. The solution: lighter weight keys and reduced friction at the posts. Perhaps the proper application of teflon and carbon fiber would help.
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Author: Tim P
Date: 2004-03-25 15:56
dave
i will read book
i will look up "overpressure"
i will work on my typing skills
i am out of here
timp
(also in way over my head.)
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Author: Mark Charette
Date: 2004-03-25 16:11
And, when it comes to nodes/antinodes - they make all the difference in a resonant system when it comes to pressure. Dave has all the right formulae for steady-state flow systems, but the airflow (air velocity) in the clarinet is miniscule. In fact, if it wasn't for the necessity of keeping air flowing past the reed to make it vibrate (and create a pressure wave) there'd be no need for any airflow. Think of replacing the reed with a small loudspeaker sealed to a mouthpiece. It might sound hideous, but the acoustic principles inherent in the clarinet would remain the same (and I'll bet I could lift the lower pads on a bass clarinet with the amount of pressure generated at the resonant nodes if the spring was too weak).
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Author: thomas.b
Date: 2004-03-25 21:01
Yes, Mark, you are perfectly right. (but I prefer the reed for creating the sound...)
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Author: Gordon (NZ)
Date: 2004-03-25 22:29
Now an attempt in layman's language, because I don't know the acoustic jargon anyway....
Don, what you say is true of NON-vibrating air.
It is the vibrating of the air that lifts a pad. Take off your register key and FEEL the vibration of the air in and out of the vent. place a membrane of paper there and SEE it.
With a bass instrument, there is a lot of energy in that vibration. Just like a bass guitar or bass piano string, the amplitude is quite significant.
Like waves on a beach, the vibrating air repeatedly hits a pad. For any given note , this will be more pronounced in certain parts of the bore. Although the air is barely travelling down the bore (as you say), the vibrating kicks a pad, then withdraws, then kicks it again.... repeatedly, many times a second, depending on the frequency of the note. Like waves smashing against a sea wall.
It is this vibration 'kicking' the pad that can cause the key to lift against a weak spring. This lifting is VISIBLE on a bass clarinet, as it is on a sax, for certain keys such as a weakly-sprung alternate F, when playing low notes loud on a sax.
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