There have been so many theories about why Stradivari and Guarneri violins are special....ground ( primer), varnish, wood, asymmetry, age etc. etc. And these sort of claims pop up with regularity, one theory is that this is an attempt to gain publicity. The test conditions are also highly unscientific, and the players don't have much time to get to know the instrument. Furthermore, a violin that might sound nice in a smallish room is not necessarily what soloists look for, they want something which has the power to be heard, above the sound of the orchestra, at the back of the hall. They want something which has the capability to respond but it is their job to get the sound they want out of the instrument.
