Thanks for letting me know about the "concern" about tweaking. What a mental jungle it is out there amongst these people!

Here's some info for you ( and them, if you care to forward ).  The bottom line is that within the world of physical science ( devoid of opinion ), it is ABSOLUTELY IMPOSSIBLE to make any two objects 100 % identical. Every piece of brass has similar yet different molecular structure. There are countless variables, minute tho they may be, in the construction of each and every object on the planet. With ANY trumpet, the variables will be in the brass piece / rod that various of the parts were cut , drilled, hammered, annealed, etc., from. BTW, EVERY horn manufacturer deals with similar variables. When purchasing an instrument, people play several of the same model until they find the one that "feels better for them". It's standard procedure and there is nothing wrong with doing this. To expect every horn of the same model by whatever company to play THE SAME is nothing but ignorance of scientific information.

Each soldered joint might possibly have a minutely different amount of solder. These are done by hand and will vary just by human nature. The mounting of a bell bead could have similar variables as could ANY of the other parts. Of course, all of these do not necessarily have the same depth of affect on the way the instrument plays. 

The closer to the player, the greater the effect, usually. Maynard Ferguson used to say that "If the first 15 inches works, the whole damned thing will work!". That's not a piece of scientific fact but it does have merit to some degree. It IS NOT TRUE that the tweaking is merely opening up the venturi.  As a matter of FACT, opening the venturi can work against an optimum tweak and wreak havoc on the way the horn plays. The tweaking process that I use was developed by Bob Malone who was a major consort in the original design of the 6310Z and the 8310Z . It consists of numerous ( at times ) adjustments to various seam locations as required by the blow of the instrument. It is not possible to get all of the horns tweaked to being identical. What my goal is with the tweaking is to get each and every horn adjusted to a point where a sensible player can get the maximum efficiency out of his horn under varied circumstances. Be aware that a lesser-developed player is not likely going to have the higher levels of sensitivity regarding kinesthetic ( muscle memory ) references. Beginning thru Intermediate players usually can play just about anything that works reasonably well and is not too large or heavy for them.

When I tweak horns directly from YAMAHA and being sent on to a dealer who has ordered them to be tweaked before being put up for sale, I always tweak the horn to satisfy MY way of playing, since that is the way the instrument was originally designed.  Having said that, I can only get them "in the ball park" and not every one will play exactly the same but they will ALL PLAY WELL!  Some tweaks can take a considerable amount of time while others  require a much shorter tweak period.

If on the other hand, I have the owner of the trumpet sitting with me, I can vary the tweak to suit his or her particular approach as well as needs. People the world over all have personal variables in how and what they play. I DO NOT believe one horn is suitable for everyone so it is up to each player to be sensitive to these variations and eventually find the instrument that suits them the best, and not to buy an instrument because it has someone's name affiliated with it. 

Tweaking is not necessarily new although Bob Malone's  method is quite different than anything I had ever been aware of prior to him teaching it to me. This is not even to attempt to say that his method surpasses all others. It's just the method he and I have had the greatest amount of success with. AND, it works on ALMOST ANY brand of trumpet, not just YAMAHA. One should also be aware that horns can gradually go "out of tweak" and might need a slight re-adjustment somewhere down the line. A word of suggestion : I have moved away from using the stiff and wiry "snakes" for cleaning and am sticking close to the soft swab types of cleaners. My favorite is REKA, made in Germany, and utilizes foam balls which when wet, easily clean all of the inner tubing. The chamois swabs on a string are also excellent. These types are not as aggressive to the soft brass which can be thrown out of tweak by overly-aggressive brushing. It's sorta like brushing your teeth. Good cleaning without making your gums bleed!!

Before the entire field of internet junkie trumpeters get it all wrong and start throwing darts back and forth at each other and at US, I hope this info will clear up some of the queries regarding what happens with the tweaking process. Does every horn need it?  Maybe not. I'd say if everything feels good and you are not fighting the horn with stuffiness or restricted sound quality, you're probably fine and should leave things alone. Tweaking is NOT something that will replace your need to PRACTICE and LEARN TO PLAY!

Bobby Shew

The "Tweaker"