It’s easy to forget that wooden musical instruments are made of materials that were once part of the trunks of living trees. In their past life, their function was to transport water from the tree’s roots to its leaves. Towards this end, wood is what’s called “hygroscopic”. This means that the moisture content will change depending on the relative humidity of the surrounding air. When humidity increases, the wood absorbs moisture from the air causing the wood to expand. If the humidity decreases, it releases its water into the air and the wood shrinks. Though a fascinating marvel of the natural world, this property does present a complication for owners of musical instruments.