What's the relationship of the number of bellows to volume?

[McDouglas]

I'm wondering what is the relationship of the number of bellows to a. the volume of the instrument and b. the sustainability of a phrase?  I'm just guessing but I suppose a fine player can play with energy and expression on any instrument.

    

I've observed that English concertinas seem to range from four to six bellows.  There seems to be a correlation to cost of the instrument. (Is this generally true?)  But what is the impact on the capacity of the instrument?

Edited December 19, 2018 by McDouglas

[Rod Pearce]

22 hours ago, McDouglas said:

I'm wondering what is the relationship of the number of bellows to a. the volume of the instrument and b. the sustainability of a phrase?  I'm just guessing but I suppose a fine player can play with energy and expression on any instrument.

    

I've observed that English concertinas seem to range from four to six bellows.  There seems to be a correlation to cost of the instrument. (Is this generally true?)  But what is the impact on the capacity of the instrument?

I found this recently while I was browsing the net trying to understand more about the relationship between reed thickness and notes. It is very interesting. Have a read and see if it answers your question.

 

http://www.concertinaconnection.com/concertina%20reeds.htm

  Bellows pressure
          The airflow in a concertina is generated by expanding and contracting the bellows. The
          amount of air pressure generated is determined by the player. The more force the player
          applies to the bellows, the higher the air pressure. The size of the bellows also play a role
          in the amount of pressure that can be generated.

          If the same amount of force (F) is applied by the player, smaller bellows will generate more
          air pressure than large bellows. Pressure is the force applied by the player, divided by the
          size of the bellows: P = F : S.  This formula illustrates that the pressure generated on a
          concertina is much greater than on a full size accordion.

[Lofty]

Rod.

 

When your quote refers to the size of the bellows, it means the cross sectional area, not the number of folds which the bellows has.

 

This is a different issue from what McDouglas was asking about.

 

Steve

[Anglo-Irishman]

Steve,

You're right  - but Rod's posting makes the point that, of the two ways of increasing bellows volume, an increase in the cross-section area will affect the force needed to produce the same pressure on the reeds, whereas an increase in length (more folds) will not. 

 

Cheers,

John

[d.elliott]

The original poster asked about volume and sustainability of a phrase of music, and the impact of adding extra folds to the bellows. The only thing that changes a reed's volume is playing force. This is a constant irrespective of the number of bellows folds fitted. Worth remembering is the fact If you apply too much force you 'stall' the reeds or make them sound flat. so the limiting factors on volume are playing force (which equates to air pressure and thus air flow across a reed), and each reeds ability to handle the pressure / air flow. 

 

The extra folds do not change pressure for any given and sensible playing force, the extra folds gives more air to play with and thus more time at a particular air flow rate. So you can either play longer phrases, or the same phrase with more reeds sounding at the same time, that is, broader chords.

 

Dave

[Mikefule]

If the "diameter" of the bellows (this measurement across the flats) is the same, and the folds are the same depth (from peak to trough) then a bellows with more folds will open wider and therefore can contain more air.

 

If you open the bellows to a certain volume, then squeeze them, you will decrease the volume and increase the pressure of the air within.  Higher pressure air will generally make the reeds sound louder.

 

It follows that if you have long thin bellows at full stretch and then squeeze them by an inch, you will get less pressure, and less loudness, than if you had short fat bellows of the same total capacity at full stretch, then squeezed them by an inch.

 

However, that is not how most of us play.  Most players try to avoid running out of air in either direction and play with shortish movements somewhere around the middle of the bellows' range.  When you do this, the number of folds makes little difference if any.  Where the number of folds comes in is when you need to move the bellows a long way in or out and the tune does not give you chance to refill or empty) them.  Examples might include a long phrase, or a phrase played slowly, or when you are playing several notes simultaneously or when you are deliberately trying to play loudly.

 

There are different considerations on English and Anglo because of the unisonoric/bisonoric thing, and the fact that an experienced Anglo player learns to adjust the bellows with subtle use of the air button.  However, I suspect that long bellows make it easier for learners who may play slowly and clumsily, using more air than a faster and more delicate player.

 

Back to the original post — and please  remember that "volume" has two relevant meanings:

 

Volume (loudness) is affected by pressure.  Pressure is caused by change of volume (air contained).  It is easier to double or halve the pressure of a small volume of air.  Therefore, playing with any set of bellows, you should have them no further open than you need for the phrase if loudness is your main objective.

 

Longer bellows (more folds) will allow you to play louder for longer in one bellows direction, simply because you have more movement available.

 

Effect on capacity: if all other dimensions are identical, then more folds equals more capacity.

 

Every extra fold is several extra pieces of bellows card, bellows paper, hinges and gussets, and extra labour to produce, so of course it affects price.

 

The main benefit of longer bellows is versatility.  It's like if your car is theoretically capable of 130mph, then 90mph is less of strain than it would be in a car capable of 95 mph max.  The perfect concertinist would usually manage with smaller bellows, but how many of us are perfect?

 

 

 

 

[Richard Mellish]

I agree with most of the above, but for two reasons I believe that the change in bellows volume resulting from the change of pressure is negligible. One reason is experience: changing from push to pull doesn't instantly produce a perceptible change of distance between the ends. The other reason is that the applied force, divided by the bellows area, represents a very small fraction of atmospheric pressure.

 

(I've been playing anglo for almost 50 years but never got around to signing up here until now.)

[Anglo-Irishman]

On 12/24/2018 at 12:15 PM, Mikefule said:

It follows that if you have long thin bellows at full stretch and then squeeze them by an inch, you will get less pressure, and less loudness, than if you had short fat bellows of the same total capacity at full stretch, then squeezed them by an inch.

 

However, that is not how most of us play.

This is true, for me at least.

When I'm playing the concertina, I don't think about moving the ends in and out, nor about increasing or decreasing the contained volume of air. I think about applying a force to the bellows. More force for loud playing, less force for soft playing. The movement, and the associated increase or decrease in the contained volume of air, are incidental, and a result of air escaping or entering via the activated reeds while the force remains the same. Given the same bellows area, a good, airtight bellows with well-set-up reeds will move less than a a leaky bellows with worn pads and ill-fitting reeds, when the same force is applied.

 

Cheers,

John

[McDouglas]

Let me follow up with a follow up question.

 

I've been playing the concertina connection Jackie for a year.  It has six bellow folds.

I am exploring purchasing a vintage Wheatstone or Lachenal.  In my price range some have four folds, some five.  (The six fold instruments are generally above my budget.  Although interestingly I see some high-end instruments with only four-folds.)

 

So do you think I will experience much of a difference in moving from a six-fold EC to one that has four or five?

 

(I'm going to guess that the transition between instruments will involve more than merely the number of bellows. However I will have only a few hours to try out the instruments with someone in a different state so here I'm trying to consider how to anticipate what I may expect).

[Mikefule]

34 minutes ago, McDouglas said:

Let me follow up with a follow up question.

 

I've been playing the concertina connection Jackie for a year.  It has six bellow folds.

I am exploring purchasing a vintage Wheatstone or Lachenal.  In my price range some have four folds, some five.  (The six fold instruments are generally above my budget.  Although interestingly I see some high-end instruments with only four-folds.)

 

So do you think I will experience much of a difference in moving from a six-fold EC to one that has four or five?

 

(I'm going to guess that the transition between instruments will involve more than merely the number of bellows. However I will have only a few hours to try out the instruments with someone in a different state so here I'm trying to consider how to anticipate what I may expect).

I started on a Rochelle, which is the Anglo equivalent of a Jackie.

 

A good vintage concertina in good condition will have reeds that respond more quickly and therefore need less air.  Therefore, you cannot simply compare the number of bellows folds.

 

A vintage Wheatstone was a high quality instrument.  They would not have spoiled the ship for a ha'p'orth of tar by fitting bellows that were impractically small.

 

That said, no one ever said, "I wish I had fewer folds on my bellows."  Better to have a little in reserve than to feel that you are working within tight constraints.

 

Playing with small bellows is good for developing your technique.  Playing with bigger bellows is easier.  As always, try before you buy, because short bellows on an airtight box with responsive reeds is better than long bellows on a leaky box with unresponsive reeds.