Anatomy of a piano tuning
Unisons are comprised of the strings that make up the pitch of a note. When you play middle C for instance, there are 3 strings that are activated. To get the purest sound these strings need to be tuned exactly to each other. If they don’t match, there will be an unwanted beat. The PTG Tuning exam checks for these beats by comparing the pitch of each of the strings to each other. After a one cent tolerance, points are deducted based on pitch discrepancy. This part of the exam is in the midrange from note 28-52.
Tuning the Temperament
I tune with either equal temperament or slight modification on that one which I call the “Vibrato Temperament”. I have been using the latter for about 6 years and that is my preference.
There are different approaches to treble tuning. Some tuners stretch the top 2 octaves more than others. A 4:1 octave is one way of tuning those octaves. That type octave gives some brightness without distracting beats. A 2:1 octave sounds in tune when playing single octaves, but with double octaves the top note could sound flat to some. The flatness is very noticeable when striking a note 2 octaves down by itself and then hitting the top note. There is a tendency for the human ear to hear the top note lower than when playing octaves.
Tuning the Bass
There are some special challenges in tuning this section of the piano. Since all the beats that a tuner listens to are occurring at a slower rate then in the midrange and the treble, one has to take some additional time. Otherwise unisons can be left out of tune. Unisons are the strings that make up a note; there can be 1, 2 or 3 strings per note in the bass. The challenge is in getting the 2 and 3 string bass unisons in tune with each other. As in the treble there are different ways to tune bass octaves. In order to tell which approach works best in the bass, I play 3 octaves at the same time using both hands of course. I try to get the best blend of the various partials.
Creating a stable tuning is an art which takes years to achieve. It comes from skill in using the tuning hammer or lever and also in how the key is struck. I tend to strike the key with a hard blow rather than a light one.
I also use a slightly modified equal temperament on many grand pianos and on some verticals. I call it the vibrato temperament. It calms down the keys of F,G and C and some others. The major 3rds that comprise those keys are then more within the normal range of vibrato (in octave 3 and lower octave 4) as heard with most singers and some instruments. There are no wolf tones in any keys. The trade off is that some keys will beat faster than in equal temperament, but that works out well with keys such as F# major.
Temperaments are kind of like fonts in word processing. You can design your own font and then apply the same characteristics to all the letters of the alphabet or you select fonts that someone else designed. The same applies to temperaments except that a temperament is determined by 12 notes and then they are extended out by octaves to the rest of the keyboard.