The art of piano tuning.
I’m a first generation piano tuner / technician who has developed extensive ear training since I was a young boy. I’ve learned piano tuning is not just about understanding mathematics and pitch frequencies, using electronic devices, or listening to beating patterns each string makes when lined up with another. It’s really about the feeling a piano gives you on where it wants to be tuned.
The process of tuning requires turning over 250 tuning pins rotationally which thin, yet highly stressed steel wires (strings) are wrapped around. In order to settle the tuning pins and strings to stay where you asked them to, proper hand technique is used to finesse the flexing of the tuning pins. And it’s not as easy as it sounds.
Since every piano is equipped with approximately 250 strings, with each string being under approximately 180lbs of elastic force (think yield strength in metals), that equates to an enormous amount of stress every piano is maintaining. If you’ve already done the math, that’s about 45,000 pounds… yes… 22.5 tons. That’s why there are iron harps, called “plates”, screwed into the rim or body of the piano. That’s also where there are large beams on the backside of pianos and underneath grands. This great amount of energy is retained in the frame, some of which is compressed onto the thin, wooden spruce soundboard (the piano’s amplifier, if you will). The vibrations of the strings carry their energy to the bridges, to the soundboard, through the rim, and out into the air around the piano. All of these components contribute to the quality of sound and pitch.
Temperature, humidity, & pitch.
The best way to keep a piano in tune longer is to control humidity. If you’ll notice the two graphs above, the first one shows the larger swings in humidity and temperature. Since Connecticut summers typically have higher humidity (brought in from the ocean wind), you can see a direct correlation between high temperatures and high humidity. Yet, you’ll also notice in early January of 2023, the temperature is still high from home heating but the humidity dropped down from lack of air humidity.
Higher temperatures can hold more moisture before reaching their saturation point, so unless that dry air is supplemented with humidity, through a humidifier, this affects the piano in multiple ways.
Dry air drops the string tension due to the reduction in the curvature (called the “crown”) of the soundboard, thus dropping the piano’s pitch, or lowering it below A440.
Glue joint becomes brittle in areas of the 5,000 internal action parts which allow the keys to perform their functions
Tone quality can change from warm and mellow to brittle and harsh from lack of moisture found in the highly compressed felt of each hammer
Art parts can shift, causing sticking keys or loose parts/screw joints
Tuning pins can weaken due to reduction in wood girth in the pinblock (multi-laminate hard maple wood which holds every tuning pin underneath or behind the cast-iron plate), causing permanent damage to the piano’s structural integrity.
To sum it up, to control humidity at a specific level (42%), you can greatly prolong the in-tonality, or tuning stability. If you keep the humidity controlled more around the piano, you also prolong its life.