Very interesting stuff from chet w regarding the maturation of wood. However, regardless of any permanent change caused by playing the instrument, there is also a temporary change. For example, I think I remember the case of a Stradivarius violin that was kidnapped and held for ransom a few years ago. I believe it went unplayed for about five months and when the violin was recovered, the owner commented that it would be a while (a month?) before the violin recovered it's normal tonal quality.