If your original claim was “Why, the quality of a strad is so obvious, anyone can instantly hear one and know why they are so revered”, then yes, you should be grabbing people off the street. If it was “Yes, we admit that modern violins are very good, but, to a trained ear, the strad will always be a step above”, then yes, you should be choosing people with such a trained ear. I still don’t think you’ve made a distinction either way at present.
We choose some hugely popular and presumably unoffensive piece that also allows us to show of the range and subtely of the instruments. Being someone that plays no musical instrument whatsoever, take my suggestion completely as uninformed but I would submit that “Four Seasons” by Vivaldi would be a good piece.
The violinist will be playing the same piece twice over, if you hate both pieces, then you should be prejudiced against the violins equally.
Firstly, your blindfolded so you can’t see the beauty of the instrument. But, also, your arguing against a false positive result in which there is a strong preference shown but not because of the inherent qualities of the violin. A single performance isn’t enough to establish if the strad is superior, only to establish that both are equal if thats the way the preferences run. If it were the case that the audience strongly preferred one instrument, then further tests would be warranted with different performers and different orders and different songs. If it turned out that in every single case the strad was chosen, then a case could be made that the strad is indeed superior. If, however, in every performance, there was always a strong preference but it was split evenly between the strad and the modern, then it would indicate that factors other than the violin are what are really important to the performance and our test procedure isn’t senstive enough to determine which is superior. But it also means that your just as likely to hear a bad performance on a strad as a good performance on a modern so theres no point trying to find out anyway.
I wouldn’t conduct the test like this since it introduces another unknown variable.
It may be quite hard for non-sceptics to grasp but there is a clear and consistent trend in human behaviour to genuinely believe something to be the case just because everyone else says it is. Especially for something like music, just by knowing your playing a strad can make the music sound better even though the sound waves coming out of the thing are exactly the same.
PS: A slightly simpler version of the single blind that avoids some of the problems proposed would be to arrange it so that 1/2 the audience to a concert are told that the violin being played is a strad while 1/2 are not told anything. Then, have them rate the performance and see how big a difference there was. While it doesn’t show how a strad might compare to a modern, at least it would demonstrate the power of pre-conception on our listening ability.