[ubernostrum]

Unfortunately what it's going to take is a Randi-style "tell me, die-hard believer, the conditions under which you would accept a conclusion of not being able to tell the difference, and we'll set it up" experiment. And really it will take one per die-hard believer.

But the simple fact is that the die-hards are going to, well, die hard. The result with violins is not at all suspect; it's very much in line with results from other fields where particular products are touted as easily distinguishable due to their inherently much-higher quality. See fine wines for another example.