Instruments need to be calibrated constantly to ensure their proper working order, and to maintain the delicate balance that exists. There are a number of specific instruments that need to be calibrated, such as high quality pianos, accordions, and even saxophones. If proper care is not taken to ensure they are maintained, problems with the quality of the sound they produce occurs. This can be avoided though by understanding how they function, and periodically having them inspected. You can hire someone qualified to do this for you, or you can learn the ways to perform this yourself.
The parts in each instrument are needed for the reproduction of sound, and when the items are initially built they undergo rigorous testing to meet the quality standards in place by the institution. Only trained personnel are given permission to calibrate each instrument, as anything wrong with the delicate balance will result in an unplayable device. Anything that is misaligned, or out of place, will inevitably result in a sound no one wants to hear. You can of course learn how to calibrate an instrument yourself, though it is often a better idea to simply have someone qualified perform this maintenance so that everything turns out the way you want.
When musical devices are initially setup, they take each part of the device and meticulously assemble it into the instrument so the sound matches what the people purchasing it intend. Room for error is not tolerated and careful thought must be put into the work. It is advised that you only ever open an instrument you fully understand so that it remains balanced. You can find resources in books and online that can help you learn how this process is done. If you decide to research this information you should still consult with someone knowledgeable in the device.
Each item you work with will be fundamentally different then any other device, so taking the time to learn about the proper calibration techniques needed should be a top priority. The procedure to work on each instrument is related to the natural complexity of the device, and pianos, accordions, and saxophones play wonderful music with an experienced player. Every instrument has a purpose, and each one of these require years of practice but the benefits are often worth the time. When a musical instrument is well maintained and properly taken care of it can be well worth it.