SOUND INTERACTIONS OFF THE REEDS
By Sean Folsom
This is a step by step time-line explanation about about some empirical research of mine on what happens inside the stock and bags and their interactions with all of the reed vibrations while playing many different bagpipes.
In February, 1973, I was staying for a week with pipe maker Colin Ross while he tuned up a North Umbriam small pipes that I bought from him for 90 pounds sterling. Colin mentioned an effect that he noticed with the neck of the bag being pinched closed which depending on the flexibility of the neck, through the use of a very thin leather bag.
You can cut off the air supply to the chanter by twisting the neck closed in order to tune the drones. Having done that repeatedly over time, there was a noticeable tendency to have this thin leather neck collapse during play, when not wanted by the piper, of course. Colin's initial fix he thought of, was to insert a small section of a small diameter green plastic garden hose into the neck of the bag. As for a good flow of air to the chanter, there was ample air, but now the scale of the chanter was horribly out of tune.
Colin explained this effect by saying saying that he thought that there was a back pressure wave or vibration from the Chanter reed, that were going back into the bag, that wave or vibration must not be interfered with. Colin removed the hose and everything returned to normal. Colin recommended that the bag be made out of leather that was a thicker than glove leather (leather weight is measured in oz.s per sq. inch. Thus 2 oz leather can be used to good effect.)
Colin recommended merely pinching the neck between the left thumb and fore finger, but not rotating or twisting the neck of the bag in a 180 degree or even a 360 degree windmill manner as some North Unbrian small pipes pipers were wont to do. Note also that this method was also used on the old style Irish pipes chanter stock which was short wood section tied into the neck opening like the North Unbrian small pipes chanter stock to silence the chanter to tune the drones (these are the bags without a more modern style 19th century chanter stock configuration.)
I also observed this method of cut-off being used on Hungarian/Macedonian/Bulgarian bass drones where the goat skin fore leg is rotated to a 360 degree to shut off the drone in order to hear the keynote of the chanter more clearly, in preparation to tune the drone. Please note: As to the Hungarian duda, if you walk playing, you have to place the bass drone between the horns of the goat head chanter stock, otherwise pressure pressure changes changes as the fore leg with the bass drone attached goes up and down in pitch as the drone swings like a pendulum with each walking step, “Wah wah Wah wah” etc.
Next, in April 1973 I met up with Dennis Brooks who lived in Berkeley, California (he now in Ireland) and got to play his Irish pipes. I noticed two effects right away: The air column inside the chanter vibrated under my fingers like some kind of massage machine and I also noticed (under my left arm) a vibration from the interior of the bag at the same time.
Dennis explained that he, by sheer luck, had found a size of bag that had a cubic volume air “coupled” with the chanter in such a way that created this vibration of these two parts. All I could say to that was, “Wow”!
I have felt the same interactions on Paddy Keenan's set of pipes as well which I have played in Dublin in 1975 and later in California in 1994.
Now, turning to my experiences with two Polish pipes, Drava River Croatian pipes and Tibor Koblicek's Slovack gajdy (in 2009), in the early 1980s, I found that if the goat head stock is not of just the right interior diameter, or conversely, the bass drone stock is not of a sufficiently small enough interior diameter air inlet hole, there will be a wolf tone to myself, whilst making and tying in a new bag for my Wielkopolska duda. When I took the Bass drone stock out of the bag I noticed how the bass was “cup bored” i.e. a large interior diameter to accept the tenon of the bass drone at the stock distal end, with a machined closure wall, with a small inlet hole, facing or presenting, to the interior of the bag.
I had seen these kinds of cup bored stocks before, on my Old Spanish gaita, and I had removed these small inlet holes with a drill and a file, out to the larger I.D. without seeming to effect any tuning adversely. I though that the stocks were made that way to capture any loose reeds that had fallen out of their reed seats, and thus, would keep the reeds from falling further into the interior of the bag itself. Note that most modern Spanish gaita stocks have large interior diameter holes all the way through, no closure walls.
In the case of this Polish pipe, I though “here's an opportunity to get more air to the bass drone”. So, I reamed out the inlet hole by several sizes and put the pipe and the new bag back back together and found to my dismay, that I now had a Wolf Tone on the 6th of the scale. I then took the bass drone stock out of the bag and plugged the stocked inlet with a wine bottle cork and made a very small hole through the cork, equal to what the diameter of the inlet was before I ruined it. Thus restoring everything back to normal.
In the cases of the Zakopane Koza, the Slovack Gajdyetc. Where I was getting this Wolf Tone problem from the maker, I made an oval out of thin plastic sheet (hobby shop) with a small inlet hole drilled in the center, and glued this baffle on the back of the goat head stock, where it faced the interior of the bag, and starting with this small inlet hole, I would increase the diameter until I got the Wolf Tone again and than I would glue a small piece of plastic over the inlet hole to reduce it's diameter just a bit back to the size where no Wolf Tone is present. I have found this to be a consistent fix for this problem and it has to do with the wave off the chanter interacting with the wave off the bass drone.
I will get into piggy back drone stocks on my D set of Irish pipes, the same problems with piggy back drones on the Dudelsacken, the French Cabrette d'Auvergne etc. and the wonderful “locked in” or “entrained” sound of a hollow main stock on Irish pipes with all 3 of the drone reeds sharing the same air space.
Let me know what you pipers think about all this, it would be interesting to read your comments. firstname.lastname@example.org
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