In May, Roberto Díaz performed at the US Library of Congress using a rare viola made by Antonio Stradivari in 1690. Called the Tuscan-Medici viola, it is now valued at $30 million, possibly the ...

If you have a trained ear-or just a strong sense of music and tone-it's easy to hear the difference between a cheap instrument and a well-made model built to resonate across the world's greatest ...