Here’s one example.
Aside from cracks like the one shown here, the critical geometry is completely affected, making any setup adjustments extremely difficult. In addition to this, the entire structure of the instrument is under abnormal tension. There are many different pieces of wood glued together inside a guitar, with grain lines pointing in all different directions. When these various components in the instrument dry out, they contract in different directions. This creates undo tension throughout the structure of the body and it doesn’t play or sound the same.
It’s true that not all guitars or string instruments need the be humidified to prevent cracks or “visible” damage. However, when someone brings me a guitar that is dried out, even if they are happy enough with it’s playability, the damage is visible to me.
Some people say “shouldn’t a dry piece of wood sound better than a wet piece of wood?” The simplest answer to this is frankly NO! Not when it’s so dry that it’s cracking and causing the guitar to change it’s shape. Guitars sound best when kept in the sweet spot of 40% – 50% relative humidity, where the guitar can be in it’s most comfortable, resonant state.
I’ve also seen many older instrument that have been dry for a long time. Some say the guitar has been “acclimated.” Rarely can a guitar be properly “acclimated.” Some older instruments don’t show many signs of extreme trauma, but none are in great condition. Most have had crack repairs and other work done to remedy the effects of being turned into guitar-jerky.
Always keep in mind, a guitar with the correct geometry, kept at the right humidity, will play and sound its best. Too much humidity makes the guitar play and sound horrible as well. However, too little humidity is generally more detrimental to the structural integrity of the instrument. And besides, you will never have a problem with excessive humidity if you live in northern Arizona.
For more information on humidity and how climate can effect guitars, check out our Instrument Wellness page.