There are many variables that affect the playability of your guitar.
- String tension
- How aggressively you play
A guitar is constructed of many varieties of wood which are all of different densities. Temperature and humidity will affect this as it would any other material. Over time, as these changes accumulate from the wood “moving” ever so slightly through expansion and contraction, adjustments may be necessary. This is normal and natural and to be expected sometimes.
Adjustments will assure that your instrument is playing easily and sounding the best it can.
As you can see, it is best to avoid extremes in temperature and humidity. Don’t leave you guitar in a hot car, attic, next to a fireplace, in front of a heater vent, or in direct sunlight. Don’t leave it in a damp basement or anywhere it will be exposed to a lot of moisture. Don’t expose a warm guitar to cold temperatures or a cold guitar to hot temperatures.
Since the woods in your guitar are of different densities, they will expand and contract at different rates. As a result, any of these extremes could even possibly damage your instrument causing the wood to split or crack, soften the glue that holds your guitar together, or cause the finish to develop cracks.
Your guitar is under a lot of string tension at standard pitch. It was constructed and adjusted to withstand all that tension and will last for many, many years of normal use at that tension. But if the string tension is too low, the neck may move back causing the strings to be too low or touching the frets. This will make it impossible to play with any clarity or recognizable pitch.
If for some reason you want your guitar at a very low pitch, have an instrument repair person set it up, adjust it, and re-string it for that purpose. However, you will most likely experience a lot of tone loss. Most guitars are constructed, set up, and adjusted to play at or close to standard pitch.
If the strings are too tight or way over standard pitch, it could cause the neck to move forward, raising the strings high above the fingerboard and making it very difficult to push the strings down. (Also, for your technical development, an instrument like this would be inappropriate to play on.) This will, of course, make it very difficult to play your guitar in tune because you will have to push the strings down farther and that will stretch them out of pitch. At the very least, some strings may break. At most, the tension could pull a few braces off your acoustic guitar, pull the bridge off and damage the top. Daily use of your tuner will keep your guitar at proper pitch. Also, avoiding extremes in temperature and humidity will give you the best assurance towards avoiding the above mentioned complications.
Electric or Acoustic guitar: which is easier to adjust?
Generally, well-made electric guitars and basses are easier to adjust because they not only have an adjustable truss rod, they also have adjustable bridge saddles. Most electric guitars have an adjustable bridge also. Bone or plastic nuts have to be filed to lower the string slots. If the strings need to be raised at the nut, then it will have to be raised with a shim or, even better, replaced with a new nut, filed and shaped to fit.
Well-made full-size acoustic guitars also have an adjustable truss rod. Nut adjustments are very similar to the electric guitar and bass. Unlike the electric guitar and bass, the bridge saddle is not adjustable, nor is it desirable to have and adjustable bridge saddle on a full-size acoustic guitar.
Sound is transmitted from the strings to the bridge saddle, from the saddle to the bridge, and from the bridge to the guitar top. Adjustable bridges for acoustic guitars only add unnecessary mass to the bridge and absorb sound that robs your guitar of its potential tone and volume. Notice that very expensive acoustic guitars do not have adjustable bridges.
The saddle on an acoustic guitar is adjusted somewhat like a nut in that it has to be filed and shaped, however, it has no string slots. Bone or plastic saddles can be filed from underneath to lower the strings at the bridge. If the strings need to be raised at the bridge, then a shim can be placed under the saddle or, even better, it can be replaced with a taller saddle shaped to fit.