Someone bought my book and after thanking them, I wrote them this email, which I believe adds some value to the book which was missing. The topic is stability and how to get it.
Hello Ville,
Thank you so much for buying my book.
It is older but has some good descriptions in it.
One thing missing is a good description of tuning unisons.
There are three things to keep in mind when tuning unisons.
1. We must have a technique that makes small changes in pitch and produces a stable pitch.
2. There is friction in the upper segment or Non-speaking length, NSL, (tuning pin to upper termination point) that results in a buffer between lever force and pitch change. This means when you first apply force to the tuning lever, the pitch doesn’t change right away. Also, this friction means that the tensions in the upper segment or non-speaking length (NSL) and the speaking length do not have to be exactly equal, although students are often told that is the goal. This friction and possible tension difference that produces a stable pitch, I call the tension band. Your job is to get, no leave, the NSL tension not in the middle, but a little high in the tension band. Near the middle, because the tension band narrows on hard blows. I.e. The vibration of the string causes the friction to drop and the tension band to narrow, and if the NSL tension is near the edge of the band, a hard blow will narrow the band and may leave the NSL tension outside the band and that will cause the string to slip.
Also, I say a little high from middle, because hard blows increase tension in the speaking length and that raises the tension band, so having the NSL tension a little higher than middle, means the NSL tension is more centered in the band during hard blows.
3. The tuning pin bends and twists during tuning, and when you remove the lever force on the pin, the pin then unbends and untwists. You have to imagine the effect of unbending and untwisting on the NSL tension, and try to leave it slightly high of middle in the tension band.
I know that’s a lot, but if you can get your mind around these things, you can begin to develop your own superior stability techniques.
Here a simple technique that works most of the time, and why. The description assumes an upright.
With your hammer at 12:00 or close, bring the pitch slightly high of your target, then gently lower it down until it is where you want it. For unisons this means a pure beatless unison that sounds like a single string.
What is happening:
When you raise the pitch, the NSL tension is at the top of the band, pulling it up.
When you are above the target pitch and gently bring the pitch down, the fact that the pitch is changing means the NSL tension is at the bottom of the band and bringing it down.
Now, here’s where the magic happens. After you decide you have the pitch you want, and you STILL have the force on the lever, you relax your grip on the lever. The pin untwists clockwise (because you were lowering pitch) and that brings the NSL tension up off the bottom of the tension band. The pin unbends as well, but because your lever was at 12:00, the bending is perpendicular to the string which has no effect on NSL tension.
If the string is not stable after a few hard blows, you did not leave the NSL tension in the sweet spot on the band.
If the pitch dropped, the NSL tension did not rise enough when you relax the lever force. Try putting the lever at 9:00. This adds the unbending effect to the NSL tension, rising it a bit more.
There are many more appropriate techniques you can develop yourself by keeping in mind the initial NSL tension within the tension band at the point when you have the target pitch AND before you remove the lever force, and the probable effect on NSL tension of removing the lever force.
It may seem complicated, but if you want to own stability, you need to understand everything that is happening within the tuning pin/string system re:forces, friction, and elastic deformation.
Good luck. Let me know how it goes.
Mark
