For descriptions, ordering information and links to KZread videos of all my whistles, email: jerry {at} freemanwhistles {dot} com.
How do I tweak a whistle?
Here are some of the issues with mass produced whistles:
1. There are shapes that can't be made with a mold. If there are "undercuts," the molded part will lock inside the mold and it will be impossible to open the mold without damaging the part. Because of that, compromises have been made so whistleheads can be mass produced using injection molding machines.
2. Also, the hollow underneath the windway is not there for a functional reason. It is there because an injection molded plastic part must avoid large variations in wall thickness to prevent "sinking," which is the distortion caused when hot plastic cools and thicker areas shrink more than thinner areas.
3. The "step" is never correct in these whistles. The step is the position of the soundblade relative to the windway floor. If the bottom of the soundblade is above the windway floor, that is a positive step. If the bottom of the soundblade is exactly even with the windway floor, that is zero step, and if the bottom of the soundblade is below the windway floor, that is a negative step.
Here's what I do when I tweak a whistle:
~ I remove the whistlehead. With some keys of whistle, I enlarge the socket so it fits the tube correctly to be more easily tuned.
~ I fill the cavity under the windway. This helps stabilize the whistle’s response and clean up the sound. What material you use matters, I've found. Some materials that people often use (e.g., poster putty) can deaden the sound. I fill the cavity with a lattice I've developed that is acoustically transparent, but that the air stream encounters as a solid surface. That preserves the resonance to retain the birdlike brightness while reducing turbulence in the airstream.
~ In the mass produced whistleheads, where the windway floor connects with the voicing chamber, there is a square edge. That is necessary because an appropriately chamfered or rounded edge would be an undercut that would make the whistlehead impossible to remove from the mold. I correct that by working a radius onto the end of the windway floor. Different keys and models of whistles require different radii.
~ I laminate a thickness of plastic underneath the soundblade to correct the position relative to the windway floor. I also place the lamination differently in different whistles to achieve the different voicings that distinguish Bluebirds from tweaked Generations, etc. I've modeled the tweaked Generation's voicing to match as closely as possible the classic voicing of the Generation whistles that were produced between the middle 1950's and the early 1980's when Generation replaced their tooling and the whistles changed.
~ I press a brass ring around the whistlehead socket to protect it from cracking from the pressure of the tube inside. That has always been the demise of these mass produced whistles. Occasionally you see a performer playing an old Generation whistle that has electrician's tape wrapped around a cracked socket.
~ Depending on the key and model of whistle, I remove some material from one or both ends of the tonebody to bring the bell note into tune and increase the range the whistle can be tuned. Mellow Dog and Bnat, alto A tenor G, low F and low D Generation tonebodies I make myself.
It bears mention, some of these adjustments are interrelated. If I change one of them, another adjustment will need to be modified to make it work correctly. If you were to only do one or two of the tweaks, even if you could duplicate them exactly, you would not get the same result.
I hope that makes sense.
Best wishes,
Jerry Freeman