Why do pianos go out of tune?

Posted by Sarah Czarnecki on

When you sit down to play your piano, you expect your piano to sound as beautiful as it looks. Instead, your gleaming grand sounds like an old-timey saloon piano from a spaghetti western. What gives?


out of tune piano keys out of alignment


Humidity and weather

No matter what kind of acoustic piano you have, most of the inner workings are made of wood. Like any wood, it expands in warm humid weather and contracts when it’s dry and cold. It only takes a few rainy days to make the wood swell, and there’s no guarantee that everything will go back to the right place when the weather is mild. 

All 230 of your piano’s strings rest across a wooden bridge that expands and contracts in the weather. The strings are slightly different in lengths and tensions, so when this wood expands, they aren’t shifted uniformly. This is why your piano may sound sharp on hot and humid days, but flat and irregular when it dries out. Thankfully, the Dampp-Chaser system does a great job of regulating your piano’s interior climate, saving you from excessive tunings and repairs due to weather. 


Wear and tear will break down anything over time. Every time your piano’s hammer strikes a string, the steel is stressed. The more you play, the more stress the string endures, so you’ll need frequent tunings to keep up. Professional pianists know that regular tunings are imperative to keeping their instruments in tip-top shape.

Kids have a tendency to bang on piano keys, putting extra force into the hammers’ strikes. Dropped objects, cats jumping on keys, and even enthusiastic playing will put extra stress on the action and strings, too. Broken parts and interior cracks will seriously affect the sound of your piano, so if your instrument takes a lot of abuse, expect the need for extra tunings and repairs.


Is your piano more of a decoration than a musical instrument? It probably doesn’t get a regular tuning if the keys collect dust, and strings just lose tension over time. The strings’ constant tension actually pulls on the structure of the piano, and it falls out of tune. And steel does stretch, believe it or not, so old strings can become slack. The longer this goes on, the worse the problem becomes. 

If your piano is just a decorative piece, take the time to run a scale every now and then to see how it’s faring. Keep on top of tunings and it will not only look great, but it will sound amazing too.


Both new and old pianos are especially susceptible to slipping out of tune. Newly-built pianos take a while to settle and need more frequent tunings to keep them sounding their best. Be patient with brand new pianos -- soon they will relax into place and will need only routine maintenance.

The wood of older pianos has expanded and contracted so many times that it weakens over time. Just like a brand-new house creaks into place and an old one gives way to decades of pressure, the wood inside pianos changes and matures.


Pianos are fussy. They don’t like to be moved from house to house and the parts inside can get jostled around. They do need some time to settle into their new place before a tuning, so if you’ve just moved into a new house, hold off on filling up your new space with beautiful music. Your piano needs a couple of weeks to adjust to its new home, too.

Even moving a piano around inside one building can disturb its inner workings. Any movement shifts its many parts, and pianos on wheels get bumped around no matter how carefully they’re moved. Drafts and direct sunlight can bother your piano’s action, too. If your piano needs to be pushed around for performances or has no choice but to be situated directly underneath the air conditioner, keep your piano tuner’s phone number close at hand. 

It’s just one of those things!

There are almost 10,000 moving parts in a piano and each one needs to be perfectly calibrated for optimal sound. Each of your piano’s 230 strings are under 160 pounds of pressure for a total of 18 tons of tension! Over time, the sheer force on the steel wires actually pulls on the wooden structure of the piano and untwists the tuning pins. 

Given all the environmental factors impacting your piano, it’s no wonder it goes out of tune every now and then!

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