Why(how) Do Reeds Go Out Of Tune?

[richard]

Hello

 

I have a few questions about concertina reeds.

 

If to tune up a reed one removes mass from the reed, which I understand alters the balance and weight distribution of the reed from one end to the other. That would imply that over time and because it is being exercised and stressed the reed gains mass. What's with that?!

 

What is the process that changes the tuning of a reed?

 

Over a life of a reed will this process of going out of tune and being retuned eventually mean the loss of structural integrity and give the reed a kind of mortality? Like us will reeds eventually fail from being tuned and played and tuned and played, or just get more and more out of tune?

 

What does this process tell us about the level of use and stress we put on our instruments. I understand what I have heard about being deliberate and thoughtful when breaking in new reeds. But when an instrument is broken in can't it be played with skilled vigor to bring out the music? I have heard some of the great players play with a lot of subtlety, and at times use a lot of punch with the bellows to bring so much power and expressivity from their instruments. Are they hastening to eventual disintegration of their reeds? If so it must be a trade off that makes artistic sense.

 

These are questions I have.

 

Thanks,

 

Richard

[JimLucas]

If to tune up a reed one removes mass from the reed,....  That would imply that over time ... the reed gains mass.

<{POST_SNAPBACK}>

No it doesn't.

 

You seem to be assuming that loss or gain of mass is the only thing that can affect the tuning of a reed, which is not true.

 

The usual means of tuning a reed involves removing mass, both for tuning up and for tuning down. The resulting effect depends on which part of the reed the mass is removed from.

 

The reed is a vibrating spring, and the parameters affecting the frequency of vibration are the distributions of mass, stiffness, and elasticity along the length of the reed. The latter two properties are affected by the crystalline structure of the metal, which can be altered by repeated flexing, an effect usually referred to as "work hardening". High heat can also affect the crystalline structure, but by "high" I mean temperatures generated by improper use of a grinding wheel, far above those developed in a closed car on a hot summer day. Changes in mass distribution are normally due to explicit mechanical effects, such as filing, scratching, grinding, or adding drops of solder. That last one adds mass, but note that the stiffness and elasticity of solder are also quite different from the steel or brass the reed is made of.

 

The fact is that quality concertina reeds don't go out of tune either readily or by very much unless they suffer mechanical damage. They certainly don't accumulate extra mass from thin -- or even thick, smoky -- air. Rust can alter the tuning, but even in that case I believe the effect results almost entirely from the stiffness of the oxide, not from any added mass of the oxygen molecules. A well played but well cared for concertina with quality steel reeds can easily go for decades without needing any retuning. Brass reeds are more prone to going out of tune than steel reeds, because they are more prone to work hardening from the repeated flexing which is the vibration of the reed, but even brass reeds should survive decades with needing major retuning.

 

I have heard some of the great players play with a lot of subtlety, and at times use a lot of punch with the bellows to bring so much power and expressivity from their instruments. Are they hastening to eventual disintegration of their reeds?

Have you ever heard of any player whose reeds have disintegrated? If they are hastening the "disintegration", I think that reducing a good steel reed's "integrated" lifetime from 100,000 years to 99,000 -- or even to 5,000 -- isn't likely to be a significant concern to a contemporary performer.

 

If so it must be a trade off that makes artistic sense.

But it's not "so", so there's no "trade off", and nothing to "make sense" of.

Edited May 15, 2005 by JimLucas

[Frank Edgley]

Just a short story which may add to the discussion. Years ago, I noticed one of the reeds on my Dipper was a bit out of tune. I checked it on the tuner and it was a bit out---5 cents, or so, I think. I took the instrument apart to tune it. I noticed that the reed tongue seemed a bit grey. I wiped it with my thumb and it came off. Wondering whether the tuning might be affected, I put the instrument back together, and to my surprise, it was now in tune! I am not a smoker, so the grey material must have come from my playing environment. In any case it seems to have been the cause of my out-of-tune reed.

[Stephen Chambers]

I am not a smoker, so the grey material must have come from my playing environment. In any case it seems to have been the cause of my out-of-tune reed.

<{POST_SNAPBACK}>

I was going to comment that reeds do indeed gain mass sometimes, but (as Frank has described) it is because of the smoky environment in which they are often played.

 

It seems that tobacco smoke can leave a sticky residue on the reeds, to which particles of dust then adhere, throwing the instrument out of tune.

 

The moral of this story :

 

If your concertina must smoke, make sure it doesn't inhale !

[Richard Morse]

One of the most common reasons for a reed to "go out of tune" is due to changes in its valve. As valves age, they tend to become more flexible (initially, and after many years get stiffer) and pull away slightly from the area where they are secured. This affects the amount of air that passes by the reed and the amount the reed is able to swing - effecting the reed's pitch. Whenever a vavle is changed the reed vitually always has to be retuned due to the restriction differences between the old and new valve (often about 5 cents).