Sit behind the wheel of your car and you can expect that it will drive pretty much the same way that it drove the day before — and the year before. It’s only when you take it for a service and the mechanic changes the brake pads or replaces the tires that you feel the difference and notice how much it’s changed.
The same is true of a piano.
Like a car, a piano changes over time, and that change happens so slowly that you don’t notice what’s happened until a service brings it back to life.
The biggest change happens to the soundboard, a sheet of wood about three-eighths of an inch thick over which the strings pass. The soundboard is just slightly curved so that the bridge presses tightly against the strings.
Humid weather causes the soundboard to thicken. It pushes harder against the bridge which puts extra pressure on the strings. As the strings are stretched, the pitch rises and because the crown will rise highest in the middle, the pitch will change more in the middle octaves than it will for treble notes and for bass.
Similarly, the opposite process works during dry weather. The soundboard shrinks a little, the crown drops and pressure on the bridge falls. When that happens, the pitch lowers, especially for the notes in the center of the keyboard.
Your Piano Will Never Be the Same Again
And the change is permanent. Even if the humidity levels return to their original state, all of that squeezing and stretching will have changed the pitch of the strings so that they don’t return exactly to the levels they once had.
Humidity isn’t the only factor that will affect the way your piano plays. All of that bashing of the hammers against the strings will wear down the parts, affecting the piano’s voicing and its regulation. As the felt at the end of the hammers is worn away and pushed down, and as the parts that connect the keys to the hammers are used repetitively, the piano loses volume and tone. You’ll notice the change most when you play quietly.
It’s all complicated stuff but a piano is a complicated thing and despite its size and weight, it’s also a fragile thing. Every time you play your piano, you change its settings just a little. Even on days you don’t play it, the weather changes the pitch of the strings.
Looking after your instrument will help you to minimize those changes. It can also help to lengthen the time you can take between tunings, when a piano technician won’t just reset the strings, but also adjust the regulation and repair the voicing. But most importantly it will ensure that the sound you want to play is the sound you wanted to hear whatever the weather has been doing.
Fail to keep your instrument’s wear and tear in mind and you won’t know anything about it until after you get the full service.