Using the bridle to achieve good tone when setting up reeds

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Using the bridle to achieve good tone when setting up reeds

Postby KimBull » Tue Apr 14, 2015 7:17 pm

Being new to chanter reed making I thought I'd share my thoughts on how I use the bridle to help set a new reed up.

Before I started reed making, I was familiar with adjusting the bridle to set playing pressure, and also noticed it had a slight effect on pitch. Something I've really noticed this week when making reeds is that using the bridle to adjust the opening plays a key role in tone.

When I'm testing my new reeds and scraping them down, my first aim is to get some notes sounding in the chanter. These often seem to be 'left hand' notes. Once I've done this, I often find the tone is soft or dull or just 'wrong'. My next step now is to adjust the aperture with the bridle. My aim is to adjust the bridle to get some notes playing with good tone, then I scrape and sand to get the other (usually right hand and bottom) notes to match.

I've found that reeds can play at the right pressure, but with poor tone. A micro adjustment of the bridle can improve tone greatly without effecting playing pressure. If I hadn't made the connection I would had continued to scrape/sand the reed and probably not achieved the bright tone I'm looking for, and perhaps end up throwing the reed out. Indeed, I've gone back to some of my early reeds which had poor tone and by making a small bridle adjustment improved them significantly.

While experienced reed makers may do this already, it was new to me and perhaps to others so worth sharing.
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Re: Using the bridle to achieve good tone when setting up re

Postby Silversmith » Wed Apr 15, 2015 4:58 pm

I think it is good to aim for a reed that doesn't require that the bridle will be needed to close the eye but simply stabalise the reed. Having said that NSP reeds are so delicate that as you say Kim the slightest adjustment of the bridle has a massive affect.
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Full Name: John Ross

Re: Using the bridle to achieve good tone when setting up re

Postby andymay » Tue May 05, 2015 6:32 pm

There's a very useful concept described in Benade's book in the section on woodwind instruments - the concept of 'equivalent volume' of a reed. This is a slightly more scientific version of what we vaguely mean when we talk about the 'power' of a reed. Basically 2 things make up the equivalent volume - actual physical size of the reed, and the extent to which the blades are scraped. More scraping = more volume. The notion is that the equivalent volume determines the playing frequency of the reed, and that there is a particular playing frequency which will be best for any specific air column. This doesn't mean there will be only one solution to creating the ideal reed for each air column. A large, open, stiff reed could play nicely and in tune in the same chanter as a small, very scraped one, although their character will be different, and probably also the pressure required to play them.

(As an aside, with a tapered column it's possible to plot out the bore, and extend the cone to its tip. Then you can measure the length of the missing part of the cone, and calculate its playing frequency. Then you can make your reed to play at that frequency! Yay!)

Anyway, back to what i was trying to get at - it's quite convenient to think of a trade off between scraping and actual cavity size within the reed. If you want to see how a reed might behave were it scraped more, try opening it a bit. You can then check out any changes in pitch/tone/tuning (to an extent) without doing anything you can't reverse. (Of course the reed will use more air though) Likewise if the reed sounds great when open but is using too much air, then closing, combined with scraping, should give a good result. Conversly if you're having to scrape a reed so much for a particular chanter that it becomes spongey and horrible, maybe a physically larger reed would be helpful.

Maybe this explains a bit what you're finding Kim? If the equivalent volume is too small - i.e. the reed is too stiff or too closed - it does seem generally that it's the lower notes which go awry. And sometimes something in the middle like the 'e'. Opening/scraping increases the EV to something which suits the chanter design better.

Myself i find there's a sound when you draw gently through a reed which gives a breathy note, and then a hint of a lower octave note. I like to have my reeds scraped enough, and just set open enough, to do this, as it seems to give a good sound in the chanter. If the playing pressure is then too high, it's probably a matter of closing and scraping/sanding to keep the EV large enough to give that low octave to the crow.

Haha this ended up a long post. And of course, i'm not saying that this is what is happening in the reed, more that i found this equivalent volume concept helpful in understanding their behaviour!

Good luck
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Re: Using the bridle to achieve good tone when setting up re

Postby pipemakermike » Wed May 06, 2015 9:05 am

Hi Andy

Very interesting stuff. It strikes me that there are a number elements that make up the internal volume of the reed:-
    length of the blade (bridle to tip).
    width of the blade.
    size of the eye of the staple.
    tip opening.
Do you have any thoughts on the relative importance of each of these. I have always felt that the width of the blade drives the sound volume and I think that I see that longer blades usually give the better sound.
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Re: Using the bridle to achieve good tone when setting up re

Postby KimBull » Sun May 10, 2015 9:46 am

Brilliant Andy! That really helps me understand what appears to be happening. So here's my current understanding-

1. Having assembled a reed, the initial work is done to thin the tips and the blades just enough to allow them to vibrate in the column of air and get the 'mechanics' of the reed working (some adjustment of the aperture at the lips may be necessary to achieve this too).

2. The reed possibly has sufficient internal volume, but lacks 'equivalent volume' because it is not flexible enough at this stage. Scraping the blades will make them more flexible and a crow will be achieved. But because stiffer blades resonate at a higher frequency, if this reed were tested in a chanter, only the higher frequency (top) notes would sound.

3. Further scraping is required to increase the flexibility of the blades (and the 'equivalent volume'). More flexible blades mean the vibration frequency will drop, and lower frequency equals lower notes, so the notes at the bottom end of the chanter will appear (I've referred to this as "scraping to chase the squeaking down the chanter" in previous posts). Andy's method of scraping and test sucking until the lower octave (low frequency) note is detected appears to be the same thing.

Too much scraping would increase the equivalent volume, but could also lower the frequency to the extent that the higher frequency notes would be lost. Initially, these would start to go out of tune. Perhaps they could be rectified by reducing the equivalent volume ie close the bridle? Ultimately, there's a point of no return and a reed scraped too thinly will resonate with a lower frequency, lose it's higher frequencies altogether and sound flat.

I've noticed the comments by John above and others on Bills thread on the FB page about the role of the bridle with interest, in particular the references to blade tension. When constructing the reed, the reed slip has a curve of a certain radius. When it is tied to the staple, the radius of that section is tightened/reduced. However, the radius at the lips is increased because it presses against the opposite blade.

Clearly (in my mind anyway!), the reed is under tension when this is done, and this tension is maintained by the binding. Now, to finish the reed the lips must be thinned and the blade scraped to achieve points 1,2 and 3 above. Scraping the reed will reduce its elasticity and one result could be a reduction in the size of the aperture .Other factors influence this such as the relationship between slip dimensions and the hardness/softness of the cane (rigidity/elasticity), all of which are unpredictable when the reed is constructed.

The bridle is therefore needed to manage the opening of the lips and internal volume during the finishing process. While it might be ideal that the bridle is largely redundant, in reality, the tension needed to maintain the blend of radii is created by the binding and elasticity of the cane. As the elasticity changes as the reed is scraped, but the binding is fixed the balance of tension is upset, so I'd have thought this ideal would be elusive.
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