alex_holden

It's probably less of a problem if your only bisonoric buttons are rarely-used high notes (i.e. which consume very little air). Some of @Little John's bisonoric buttons have low bass reeds that consume a lot of air, so without using an air button to compensate I imagine you could get into trouble rather quickly.

Ah, I think maybe you meant this topic:

This sounds similar to @Little John's idea of bisonoric buttons on his Crane duets. In that case, you will almost certainly want an air button that is accessible while playing.

Hi Isel, do you mean this topic?

My understanding is traditionally the standard size for English instruments was 3/16", which is about 4.7mm. English-made Anglos with metal buttons often were 3/16" too, but if they had bone buttons they may have been more like 6mm or even 1/4" (6.35mm). Some Wheatstone Linota Anglos have 5.7mm metal-capped buttons, which I think is a comfortable compromise. Vintage cheap German instruments tended to have wooden buttons that were on the larger size, sometimes even bigger than 1/4". Modern cheap Chinese instruments are similar to the German style construction, whereas better quality modern 'hybrid' instruments tend to be closer to Anglo style construction but with accordion reeds.

Thanks @Alex West and @wunks, that's useful to see. It's interesting that although one is an anglo and the other is a duet, they have very similar reed pan layouts.

If the air button is just used for opening/closing bellows quietly, not actively used during playing, it's usually possible to fit one in somehow. It may be necessary to use a very small pad close to the centre of the action board and/or place the button somewhere awkward to reach (e.g. in the side of the handrail). I didn't put one on my first instrument but I think if I was redesigning it now I would find a way to add one. I am also curious to see how Jeffries fit 51 buttons into 6 1/4" (is that 50 notes + air?).

It's a little different because with the Müller system the end of the strap that can swivel is on the pinky side, and the thumb end is more conventionally clamped: Where would the thumb end of the strap be clamped to? The hand rail? Perhaps the strap could be free pivoting on that end too, but we do need to also have a way to adjust the length of the strap. Would it help if the rail is slightly banana-shaped, curving closer to the keyboard at the pinky end?

OK, I think I see what you mean. If you did that to both ends, presumably it would be impossible to play standing up because you need to rest one end on a leg to prevent the instrument tilting forwards?

Hi Wunks, I’m not sure I follow your proposal. Any chance of a sketch?

I think it would be tricky to implement in a strong reliable way, without adding a significant amount of weight. I wonder if a simpler alternative might be to do something different with the hand strap attachments to allow it to move more? Something like with the Müller system where the strap can rotate on the attachment point, allowing the hand more freedom of movement?

Hi Isel, do you mean a handrail that can be loosened (with a screwdriver), rotated to a different angle, and then tightened to lock it in the new position for playing? Or one that has a loose central pivot so it can rotate freely while playing? If the latter I wonder if it might make playing more difficult because the instrument would be less stable?

Thanks Tom, that's interesting and fits in with how I have been thinking about it. I have been analogising it to the operation of a hydraulic ram pump. Water flow gradually builds up, then a valve suddenly shuts and the water in the pipe leading into the pump 'piles up' and generates a large pressure spike, enough to lift a packet of water to the top of a hill. Then the pressure dissipates and the spring-loaded valve is able to open again and restart the cycle. Comparing it to a reed, air flow through the chamber and wind slot gradually builds up, then the tongue suddenly blocks the flow and the air in the chamber piles up against it, giving the tongue a large downwards kick, enough to swing it further than static bellows pressure alone could. Where my mental model got a bit fuzzy is why isn't there also an air-hammer effect acting to prevent the upward swing; my guess was because during the downward half of the cycle the tongue is partially blocking the slot, the air flow doesn't build up as high. It makes sense that as you say, there is also a more gradual cutoff as the tongue swings back up and gradually enters the vent bevel.

Hi Chris. I have come to the same conclusion about how to set a reed, however I disagree about volume coming only from the speed of air flow. My theory is that volume comes from the amplitude of the pressure pulses that happen due to the 'air hammer' effect at the instant the tongue blocks the slot. The biggest pulses will happen if both the air flow is high and the flow is interrupted as instantaneously as possible. If the top edges of the vent/bottom edges of the tongue are rounded, that would cause the flow to be interrupted more gradually, leading to a smaller pressure pulse. I also have some rough ideas about how the shape and size of the reed chamber effects the amplitude of the pressure pulses, though I have no idea how to mathematically model it.

The same question came up elsewhere recently, and I believe the conclusion was that it's a vintage Jeffries.