There is an interesting thread over on the Les Paul Forum at the moment regarding the difference in sound between a lightweight aluminium tailpiece and heavier zinc tailpiece on a Les Paul. It has been suggested that a “double-blind” test be performed on both tailpieces to determine if the majority of listeners can tell the difference between the two, and therefore determine whether it is a worthy change or not.
There are a couple of problems with this that I thought would be interesting (to me at least) to mention them here. Firstly, it will never be a perfect test as there are too many uncontrolled variables. Even if you use a brand new set of strings from the same vendor and of the same gauge, different sets can still sound different. If you use the same set of strings, then the second time they are played, they haven’t been played for the same amount of time as they had been for the original test, which will effect the sound, however small. The flip side to that of course, is that no test is perfect and there will always be variables that you cannot control.
The second problem, and the one I think is impossible to overcome, is the variable of the human ear. Some people have higher developed hearing than others and can perceive smaller changes in sound than others. This is a fundamental problem that cannot be overcome, because even if you can do a study of a large enough control group, it will never be able to quantify if the change is going to be good for you. The only way to see if you like one sound better than the other is to try it for yourself, otherwise all you are doing is using other people’s perception on what is better and that is no guarantee for yourself. If you ask someone to make a choice as to whether something sounds better than something else, you are immediately verging off of the scientific path and into the realms of speculation. The only scientifically provable criteria you can study is which frequencies are enhanced or suppressed by a specific modification and that can never tell you which is going to be “better” to your own ear.