Wood used to build musical instruments for the American market is dried to 5% to 8% moisture content, which makes it as stable as possible. Traditionally, and for centuries, musical instrument wood in Europe was dried to 15% moisture content. That works in a very temperate climate with small changes in relative humidity over the course of the year. But when those instruments are brought to the United States, they usually develop cracks and warp terribly. Now musical instrument wood is dried to the 5% to 8% standard worldwide.