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Thread: An experiment with reeds

  1. #1
    ppp Pianississmo Musicanic's Avatar
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    Apr 2017

    An experiment with reeds

    I am a restorer of organettes (small hand turned automatic reed organs) and I have been asked to convert one instrument into a double reed instrument. the instrument in question is a "Concert" roller organ. These were made in the USA from about 1880 to 1920 and play 20 reeds using small pinned wooden "cobs" to operate the keys and play the reeds. The reeds are held in a block of wood secured behind the pallet board with one reed per pallet. Our experiment involves mounting a second reed block behind the firs so that the air flows through a long channel with the two reeds mounted oen after the other. The reed block is held in a chamber which is connected to a reservoir and exhausters so that it is continuously evacuated to about 7"-10" water gauge.
    The problem I am having is trying to get the pairs of reeds beating "celeste" reliably. Some pairs work fine but others don't. I am familiar with brass reed tuning and have worked on several organettes which were originally designed as double reed instruments. The significant difference is that in all those instruments the individual reed chambers are physically separated, beyond the pallets, so that they effectively have independent air supplies. In our experiment there is not enough room to do that.
    Does anyone have enough knowledge about how air flows over and through reeds to help me understand what is going on here and why some pairs beat and others don't despite them being tuned off pitch as normal for celeste reeds.
    Musicanic, UK

  2. #2
    ff Fortissimo SubBase's Avatar
    Join Date
    Sep 2007

    one reed sitting above another should also result in one reed sounding earlier than the other, if the only wind path is past another tongue.
    There were some instruments built with double-tongue reeds, IDK if it was a celeste or not. Those reeds were 50% wider.
    Reeds in close proximity always try to "draw" each other to the same pitch, BTW, no way to overcome that except by separating their tuning much wider to force the to be out of tune, but I don't think anyone will like the sound.
    To fight the pitch-locking, maybe lower the wind to 3"? IDK if that's plausible.

  3. #3
    ppp Pianississmo Musicanic's Avatar
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    Apr 2017

    Thanks Casey, food for thought. I carried our some more tests today and found taht in some cases, although a pair was tuned to beat, when blown together one reed was "ruling the roost". I then realised that the two sets of reeds are not identical, although they both come from the same model of organette. From this I have concluded that they prefer slightly different pressures, or take different air flows, to operate at their best, so sometime one reed is better off than the other and takes over. I am looking to see if I can locate another reed set to match one of the existing.
    The reeds are not actually one above the other. The reed blocks have a dead-end chanel behind the pallet and the reed sits on the top side of that channel. In order to fit a second set I have drilled through the dead end of the channel and screwed an identical reed block on the back. The result is an extended channel from the pallet with the reeds one after the other along the top of the channel. The theory is that when the pallet opens the air will be sucked through both reeds equally and create the desired effect. Alas the theory seems to be faulty!
    The experiment continues.

  4. #4
    ppp Pianississmo Mr. Polecat's Avatar
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    Oct 2016
    Fort Seybert, WV

    I am recalling something from years ago, from college classes, but I can't quite pin it down in my mind.....

    But when you have reeds with separate air paths, then they will both be getting "clean" air, that is, a constant suction, without any oscillation or anything.

    On the other hand, if you stack the reeds, then the "underneath" one would have an oscillating pressure drawn through it (caused by the top reed), and so its amplitude would only be equal during the moments when both reeds' tunings allowed their high-pressure moments to correspond, and thus the top reed would almost always drown out the bottom one?

    I don't really know what I am talking about, and am just grasping at straws that I recollect from years ago, in fluid dynamics classes in the bad-old-days, lol. But I would think that a better way would be to figure some way to expose both reeds directly to the "clean" suction directly from the main billows. That ought to keep them from interacting with each other, at least insofar as oscillation, anyway.
    1914 Estey Parlor Organ. Guts of a 1904 Putnam Organ (parts organ). Digital stage piano. Various guitars. Autoharp. Banjo. Musical Cat.

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