Some technical information related to piano tuning is offered here.
This may include more details than some customers want to read.
However for those who love the details, see the information below.
Pitch, Inharmonicity & Tuning:
To fine-tune a piano, first the overall
tension must be correct. If it is not
correct, the instrument may need a
"pitch-raise" to establish the correct
tension and enable the instrument to
hold a tuning at concert pitch (A440).
Once the correct tension is established,
the technician must make very small
adjustments to each string to fine-tune
the instrument.
Each piano is somewhat unique due to something called "inharmonicity". In
addition to the full string length, which represents the fundamental frequency,
strings vibrate in a number of shorter sections separated by "nodes". The
nodes divide up additional related frequencies that piano tuners refer to as
partials.
Some musicians may refer to overtones or harmonics when speaking about
related topics. We won't present an argument here regarding which term is
correct (See Partials figure 2 below). However, piano tuners refer to them as
partials. These related frequencies of a tuned piano may not match up exactly
with the mathematically determined harmonic frequencies due to a number of
issues relating to the size, tension, length, materials and sometimes even
imperfections in the steel strings. (If you want a very short demonstration of
partials/harmonics, ask me during your next tuning.)
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 the unique inharmonicity characteristic of each
piano. Therefore, the technician does not simply match the strings to a given
set of pitches. Years ago there were some tuners who carried a set of 12 tuning
forks to set the initial middle octave. Experience has shown how small changes
are needed in individual pianos to adjust for the inharmonicity that is unique
for each acoustic piano. Your tuner assesses this, via listening to the interaction
among notes and partials. A slight variation is applied from the theoretical
standard to make your piano sound its best.