Why are the strings so hard to press? - Feb 2001
String tension: String thickness determines the amount of tension required to tune to a particular pitch. Thicker strings require more tension. Your fingertips must overcome that additional tension. String tension affects playability, volume & instrument health (read about neck warping/rotation & bridge lifting below).
String-to-fingerboard distance, or action.
High Action from Humidity: In humid air, unfinished wood inside of instruments absorbs water. Instruments swell & their bellies puff out, raising the strings & making them harder to press unlikely in winter.
High Action from Neck Warping: Over time, string tension can cause the neck to bow upward & increase the string-to-fingerboard distance & playing difficulty. Poorly made instruments & instruments strung with excessively thick strings are more prone to neck warping.
High Action from Neck Rotation: The necks of most stringed instruments are joined into a "neck block" that helps keep the fingerboard at an angle that is appropriate to playing. Just as string tension can cause the neck to bow, it can also cause the neck to rotate in the neck-block & increase the string-to-fingerboard distance (& playing difficulty). Poorly made instruments, instruments with heavy strings & instruments exposed to excessive heat are most vulnerable.
High Action from a Lifting Bridge: On flat-top acoustic guitars, the strings pull upward on the bridge. Therefore, string tension can tear the bridge loose. But before the bridge comes off, it usually lifts in the center, forms a gap between the itself & the surface of the instrument & elevates the strings. Poorly made instruments, instruments with heavy strings & instruments exposed to excessive heat are most vulnerable.
What Can I Do?
In all cases, use the lightest gauge string that produces good sound to prevent/minimize damage of your instrument caused by heavier-than-necessary, high-tension strings.
Always keep instruments in air that is as close to 50% humidity as possible to prevent swelling (too humid - 60% or more) & cracking (too dry - 40% or less - a serious risk in dry weather).
Examine your instrument's neck for straightness; have a qualified technician adjust the truss-rod (if the instrument has one) in early stages of neck warping.
If your action is high, & you're not sure why, ask a qualified repair person to check for neck rotation & lower the bridge/saddle to postpone a neck reset; have neck reset if necessary.
If gaps form under flat-top guitars' bridges; ask a qualified technician to examine/re-glue them.