1. A guitar’s sound comes out of the soundhole.
Anyone who has used one of those soundhole plugs to prevent feedback when using a pickup knows that acoustic guitars still make a lot of noise when you tape their mouths shut. The soundboard moves air both inside and outside the guitar when it is activated by string vibration, and sound travels through the spruce as well. Most folks agree that a guitar sounds better when the soundhole is open, however.
2. Cracks in the top of a guitar ruin the sound.
Actually, lots of people are afraid cracks anywhere in a guitar hurt the sound. Believe it or not, multiple cracks in the soundboard of a guitar will not harm the sound at all if repaired properly, unless they’ve caused loose braces or other structural weakness. While cracks in the back and sides should also be repaired to prevent them from spreading, they have even less effect on tone or volume. This is not to say that cracks don’t hurt the value of a guitar, however.
3. Guitar necks should always be perfectly straight.
Most guitarists find they get less fret buzz with a slight amount of “relief” (forward curve) in the neck, especially if they play hard on the bass strings in lower positions.
4. Tying your strap to the peghead (instead of a strap button on the heel) can warp the neck.
This myth is based on the belief that a guitar neck is in a state of fragile balance against the evil influence of string tension, and any additional tension must be avoided. But steel-string guitar necks are made to withstand over 150 pounds of pull from a set of light strings, so the slight weight from hanging a strap on the neck isn’t enough to worry about.