What's THE BEST Instrument Sound?

By Andrea Wallick, cellist and Andy Fein, violin maker at Fein Violins (FineViolins.com)

Have you ever heard an instrument's sound described with physical adjectives such as "dark", "bright", "rough", or "thin"? Sound doesn't produce light, and it's not a physical object, so what do these words actually mean? And more importantly, what kind of words describe a good instrument's sound? 

Rachel Barton Pine discusses the differences between Stradivaris and Guaneri del Gesus

These terms do not come out of nowhere. There are actually subtle differences in the sound composition that make terms like these universal! If two people play different violins with different bows at different volumes, obviously they will sound different. But what if the same person plays two violins with the same bow at the same volume with the same articulation? Will they still sound different? Yes, because of the instrument's timbre.