Pianos go out of tune primarily because of changes in humidity. and consistent errors have been known to result. These devices often attract the untrained operator in an endeavour to circumvent the need for formal training. Formally trained and experienced tuners often find that the use of electronic tuning devices is unnecessary important elements associated with trained aural tuners are often left out by those relying on electronic tuning devices. Some tuners use pure aural techniques while others use electronic tuning devices. A tuning hammer and tuning mutes are the main tools of the piano technician. Pianos that are more than slightly out of tune tend to be unpleasant to play and listen to, to an extent that varies with the ear of the listener. When a piano is only slightly out of tune, it loses the glowing tonal quality characteristic of a freshly tuned piano, especially because each note in the middle and upper range is sounded by more than one string, and these may get slightly out of tune with each other. The longer a piano remains out of tune, the more time and effort it will take for a technician to restore it to proper pitch. Pianos that are prized by their owners are tuned regularly, usually once every six months for domestic pianos, and always just before a performance in concert halls.
