How is a piano tuned?
The short answer is that a piano is tuned by adjusting the tension of the 230 odd strings that are stretched across its frame so that all the notes will play harmoniously at their assigned frequencies.
More specifically, there are two main techniques:
1) Tuning by ear is done by carefully listening to and adjusting the interference vibrations between the coincident partials of intervals within the musical scale. It sounds complicated, but it is really a matter of adjusting the string tension so that all of the intervals (two notes played together) "beat" in a pleasing, even progression, slower in the bass and faster in the treble.
2) Tuning with a visual aid is accomplished by carefully adjusting string tension so that the vibrational frequencies match an ideal configuration indicated by an external electronic aid or scope. Some visual aids are simple, and others as complex as modern computer technology.
Experience has proven that excellent results can be achieved employing either method. In either case there is no substitute for the care and experience of the technician. Common to both methods are techniques for settling the string and tuning pin to help preserve tuning stability, and strategy such as "rough" tuning a few times to get a very flat piano close to pitch before fine tuning.
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