I guess I should know, and I talked to someone about this a long time ago but I don’t remember. Why do you tweak a tin whistle? What is it you do (more than taking off the mouthpiece?)
Should I know?
The idea is to improve the whistle. Personally i’ve never really seen the need, outside my d whisltes most haven’t even their heads removed.
Ask not, why do you tweak?
Ask rather, how do I attain the state of tweaking, of oneness? All evil flows from these three sources: the Windway, the blade, the fipple.
Some people are not satisfied with the way whistles come to them and so they tear them apart in the hopes of making them faster, stronger, and more whistle-like than ever before.
If you still don’t understand:
Destroy any of these and you destroy the evil.
Desire destruction, and destruction will be your goal.
Desire nothing, and nothing will be your goal.
Desire not-desiring, and not-desiring will be your goal.
Not-desiring is evil overcome, windway, blade, fipple refined.
As you can see, failed attempts to tweak a favourite whistle can have a drastic effect on said whistle owners mental health. 
You could always convert from whistle to Quena, Bloomfield. Then it’s just between you and the blade! 
Cheers,
David
I usually have to always tweak waltons, oaks, generations only so that I can get a smooth transition between lower and upper octives and to eliminate the Squeakiness.
The method I use is the same as most. Place a little wall puddy in the hollow of the mouth piece. I have eliminated the use of sand paper and have gone with soft scrubb pads which tend to work better when smoothing out the edges.
The main reason I’d tweak is to correct flaws in the head casting - usually, tags of extra plastic left over from the molding process. If the whistle plays well, I don’t bother to tweak it (about half my cheap whistles are untweaked). For ones with problems, I try to do the least needed amount of work, though if I have the head off anyway I’ll generally do the blue tack in the windway trick.
Even with tweaking, not all whistles end up great (at least for me), but I can generally improve them a bit, and sometimes everything comes together and I produce a really nice one.
Of all my cheap D whistles, I’m fondest of a Generation redcap, an Oak, and a Feadog. Of the three, only the Gen was tweaked (went from “barely playable” to “really good”, though - one of my successes).
In general, I’d say “if it ain’t broke, don’t fix it”. If you want to tweak, don’t do it on your favorite, or only, whistle unless it’s got real problems. Get some practice in on whistles where you don’t have as much of an attachment, and try tweaking whistles you already like only after you’re comfortable with the process.
It has ever been the fate of greatness to be mistaken for madness.
Ummm…like, whatever.
HeySue
Back in the days of tv’s with rabbit ears, my sibs and I would be engrossed in a program, and Dad would feel compelled to come along (not during a commercial) and tweak at the antennae until he had, at least momentarily, made it worse. We’d scream of course, and he’d go off feeling under-appreciated.
Tweaking whistles, for those so compelled, seems a more benign past-time.
I got into tweaking to improve the response of the low notes on a Perri. I went on from there and have succesfully improved the sound or playability of several more, with a noted lack of sucess on a Susato VSB (have yet to do the guitar pick soundblade).
I recently successfully mash/tweaked a Clarke original and it’s turned out to be one of my favorite whistles. The problem, as noted in the tv analogy, is to know when to leave well enough alone. “There’s a fine line between clever and stupid.” - David St Hubbins
I used to feel compelled to tweak because the whistles didn’t play properly. I just recently went and bought a Gen D so I could have a completely untweaked whistle. I selected it from a number of them at the store. It sounds beautiful. The whistles don’t play better but I do. In short, make sure it is the whistle that doesn’t play well. However, if you desire to tweak have at it. Its only a 6 buck whistle. What have you got to lose?
Ron
Tweaking does a lot of things to make a whistle good.
- Readjusting the position of the head (in or out) to put it in better tune.
- Cleaning out hanging fipple ‘chads’ or small pieces of plastic created from the casting (as mentioned in the previous posting).
- Trimming, shapening, blunting, undercutting or any other change made to the blade. This is usually done to encourage the air to pass more over or under the blade depending on the design of the whistle.
- Some whistles have pockets on the block area made from casting a certain way and some of these sound better when that area is filled in with some sort of filler material.
The blade adjust does wonders for cheap whistles
For example, I bought a Clarke Woodstock at the local tractor supply store for just 3 or so dollars. The whistle flips octaves a bit unstablely and squeeks when doing a lot of rapid stuff. Taking an exacto knife and the knowledge of what whistles expect, I was able to make the octave change more stable and I was able to go up and down with lots of note transitions without it squeeking as badly as it did before.
But, the guy to get tweaked whistles from is Jerry - He is the official tweaker of the new millenium. 
I’ve never tweaked a whistle, and I have all three of the above mentioned.
Jerry tweaks whisltes professionally, but if I recall, he sent a whistle that he thought was unplayable, and Peter L not only played, but played it beautifully… or so I heard. I also think I heard something about one of his students playing it beautifully, too…
Hmm… maybe it’s the air.
If I remember correctly, it was the high manganese content in the well water. Peter has offered to send me some.
Best wishes,
Jerry
If you heard about it in [u]this thread[/u], it was a brand of whistle (Generation) that was being discussed as playable/unplayable.
Or maybe I haven’t heard the full story. Was a whistle actually sent to Peter?
Yes. I sent him an off the shelf, untweaked Generation, along with some experimental tweaked whistles I was working on. The untweaked Generation was pretty much the same as any untweaked, new Generation you might get.
Best wishes,
Jerry