Piano tuning requires a technician who has plenty of experience and training as well as a good musical ear, the right tools, and lots of patience. Here are a few fun facts about the piano tuning process.
1. For some notes, a tuner has to tune multiple strings
Larger strings are used for lower piano notes, and smaller, thinner ones for higher piano notes. The lower strings tend to have a full, rich tone because when they're played, many overtones (supporting notes mathematically related to the main note) are present and detectable in the sound, causing a complex and full-sounding tone.
For the higher notes, overtones are still present, but fewer of them are in the range of human hearing, so the tone may not sound as rich and complex initially. Using two or three strings of the same pitch is another way to help make a fuller, richer tone.
The multiple strings have to all be on the same pitch to form one unified note when you hit the piano key. However, the piano tuner has to tune them separately. This is one reason why piano tuning has to be so precise.
2. Tuning has to be done perfectly, but also imperfectly
Piano tuning is precise, but there's also a sense in which your piano has to be tuned to a precise level of imperfection to function. That's because of the physics of sound. Different musical intervals sound best when tuned in different ways. For instance, in a just intonation tuning system, when the intervals most commonly heard in chords (the interval of a third) are almost perfectly in tune, other intervals may sound less in tune.
The system of tuning typically used today for pianos is called equal temperament intonation. This tuning system is based on the interval of an octave, dividing the notes in an octave equally to ensure that each note is in tune with its counterparts above or below. This way, all your Cs will sound in tune with each other, albeit at the expense of the beautiful thirds that could be achieved with just intonation.
3. Piano tuning uses several specialized tools
Piano tuning takes specialized techniques and training, but also specialized tools. The main tool that a piano tuner uses to adjust the nuts holding the strings is called a piano tuning lever (it's also sometimes called a piano tuning wrench or piano tuning hammer). However, other tools are typically required as well to do a thorough job.
Your piano tuner will likely use an electronic tuning device to more precisely detect each note, for instance. And they'll use mutes to keep the rest of the piano strings quiet while working on a specific string. They may also need other specialized tools like a lever tip wrench and piano tuning screwdriver.
As you can see, piano tuning can be a more complex task than it appears. Get in touch with your piano tuner to learn more.