Tuning

[JerryPH]

You don't use a B&D anything... lol

Use metal files and scrapers. The smaller the reed, the smaller the modification needed to make a change.

 

[rancoman]

Glad you enjoyed my little joke!

 

[JerryPH]

:lol: :ch

 

[boxplayer4000]

Doppler Effect.
Coming from a technical background with some basic physics I am struggling with the idea that the Doppler Effect can influence note pitch. The Effect is normally associated with a moving source of sound being listened to from a stationary position (or at least from a position moving at a different speed to the source).
While experiencing the Doppler Effect it is noted that the pitch falls when the sound source approaches and rises when it is receding.
It is suggested elsewhere in this thread that the air passing over a reed and escaping serves to create the effect of the moving object; an object moving away when the air is escaping and presumably by the same logic an object approaching when the air flow is reversed.
If the Doppler Effect is affecting reed pitch then surely in an accordion situation where the air flow is constantly reversing then the pitch will rise and fall. This is not being suggested in the thread.
Furthermore if escaping air gives the effect of the sound source moving away then the Doppler Effect will be to raise the pitch but it is suggested that blowing hard into, say a recorder, lowers the pitch which seems to be the opposite of the Effect.
It is also suggested earlier that the Doppler Effect comes into play when mouth organ (or harp) players cup their hands over the escaping air. I believe this is simply the reed responding to reduced air flow in the same way that some bag-pipers slur their notes by restricting air flow or even accordionists getting the same effect by only partially pressing the key.
I believe the reasons why reed pitch rise and fall with air pressure is complex and varied. Why do some rise in pitch with increased pressure while others fall?
(This is for discussion only but I’m off to put on my hardhat and flak jacket in any case.)

 

[debra]

There is a lot I still do not understand about everything that influences note pitch on the accordion. A lot of things have very minor influence, but still measurable. For instance, When I play a note in the L register and then switch to the LM register the pitch of the L reed changes a little bit. When I play a note and then remove one of the bellow pins (or screws) the pitch of the note changes. When you partially close the pallet but maintain the same force on the bellows the pitch does not change significantly but when you increase pressure at the same time the pitch goes down. In both cases the shape of the "resonance chamber" including the position of the pallet all remains the same. The only thing that changes in all of these cases is the airflow. WIth pitch bending the airflow changes dramatically: the air has to go through a smaller hole, which means air moving much faster than when the pallet is fully open.
Many accordions seem to be relatively "stable" in the sense that note pitch does not change enough for you to hear the difference when you change the register or when you remove/insert a bellow pin. But all accordions are "instable" enough to change pitch significantly when you remove the "opposite" valve which disturbs the airflow very close to the reed that plays.

An interesting experiment (which I cannot perform) would be to have a high-speed camera aimed at a reed to see whether the actual frequency of the reed changes during pitch bending, and whether it changes as much as what the listener ends up hearing. I believe that the actual frequency does not change as much as what we hear, and that the way in which the vibrating air stream changes speed (after exiting the reed block) explains at least part of what we hear (through the Doppler effect). But I could be completely mistaken. Too bad that it is so hard to measure what is really going on. Musicians tend to not also be physicists and although I have a degree that entitles me to teach high-school physics I do not feel qualified. Maybe I should ask a friend accordionist who has a PhD in physics...

 

[Glenn]

The Doppler effect is the pitch perceived by the listener as a result of the speed of the wavefront at the listener. Thus a siren approaching has the speed of the vehicle added to the wavefront as it hits the listener, hence the frequency is perceived as higher than when the vehicle passes and its speed is subtracted from the wavefront. That this can happen in an accordion I doubt. What I can very well imagine are quite complex interactions of air pressures and energy transfers between vibrating "objects" in an accordion. This will have some effects on the fundamental reed vibrations and it's harmonics. This is where the "magic" is rather than Doppler I believe.


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