A common question is "How often should my piano be tuned?" The textbook answer is "every six months". However, key factors are temperature, humidity, location, room environmental controls, piano age, usage, and discerning preferences of the piano players. Some pianos go out of tune significantly in less than six months while other instruments hold fairly sold for a year. Over time your technician can help you determine the optimal tuning schedule.
The Tempered Scale:
An equal temperament refers to the intervals between notes on the musical scale within an octave. It may also be a term used to refer to a system of tuning. When a piano has been tuned using an equal temperament, the octave intervals have been divided into smaller equal steps, each having equal frequency ratios between the adjacent notes. These are the smallest interval in the tempered scale that is used in common classical and Western music. Each of these intervals are 1/12 the width of the octave and are referred to as a semitone or half-
Pitch, Inharmonicity & Tuning:
Each piano is somewhat unique due to something called "inharmonicity". In addition to the full string length (the fundamental frequency), strings vibrate in a number of shorter sections separated by "nodes". The nodes divide up additional related frequencies that may be referred to as overtones, partials or harmonics. (We won't present an argument here regarding which term is correct.) These related frequencies may not match up exactly with the mathematically determined harmonic frequencies due to a number of issues relating
The "scale" of the piano, the design that includes string length, diameter, materials, and tension, also impacts the inharmonicity and tuning approach. The tuner must deal with this unique "inharmonicity" in each piano. Therefore, the technician does not simply match the strings to a given set of pitches. The inherent inharmonicity is different in each acoustic piano. Your tuner assesses this, via listening to the interaction among notes, and a slight variation is applied from the theoretical standard to make your piano sound its best.