<HTML>We all have to deal with customers asking why pianos g= o out of tune. Sometimes customers do not understand why a piano goes out of= tune, or blames you for doing a b ad jib, when there is a drastic change in= the weather. That is why I've written an article, that, I think, explains i= n layman's terms why a piano goes out of tune. I've copied the article below= . I hand a customer the article when they ask questions. Comments are welcom= ed. (You're welcome to copy the article and use it). Wim Why does a piano go out of tune? By Willem Blees RPT Have you ever noticed how a piano seemed to go out of tune, but then shortly= thereafter, it sounded better again? Blame it on the changes in the weather= . It's the changes in temperature and humidity that cause a piano to go out = of tune.  This article explains exactly what goes on inside a piano tha= t causes this to happen. A piano is made out of wood, steel and cast iron. On a grand piano, when you= lift up the lid, you can see the strings, which are made out of steel. The = strings are attached to the cast iron plate, which is that large gold "harp"= . If you look through the strings, you will see wood.  That is called t= he soundboard. This is the soundboard that everybody worries about cracking.= (That is a topic for discussion some other time). It is this soundboard that creates all the tuning problems. Although you can= 't see it with the naked eye, the soundboard is crowned, which means it is h= igher in the middle than at the edges.  To give you an idea of how much= of a crown there is, if the arc of the soundboard was part of a ball, that = ball would be about 65 feet in diameter.  It is this crown that produce= s the sound of the piano. If there were no crown on a soundboard, the tone o= f the piano would be very dull. We all know that wood absorbs and releases moisture. During the moist summer= months, wood absorbs moisture and expands. This is very evident in the summ= er when you have trouble opening windows and doors. When the soundboard abso= rbs moisture, it also wants to expand. And, like a door, which expands again= st the frame, which is also expanding, the soundboard expands against the si= des of the case. But because the soundboard cannot expand outwards, and beca= use it is crowned, the only way the soundboard can expand is for the middle = to go up. When you look inside the grand piano, you will see that the strings cross ov= er a long piece of wood with little pins sticking out of it. This long piece= of wood is called the bridge. The bridge transfers the vibrations of the st= rings, which are set in motion by the hammers, to the soundboard, which in t= urn amplifies the sound of the strings. (That is basically how a piano creat= es sound).  What you cannot see, however, is that the strings actually = go up and over this bridge. In other words, if you were a flea, you would ne= ed to go up hill to get to the bridge and down hill once you have crossed ov= er the bridge. Since the bridge is attached to the soundboard, and the strings cross over t= he bridge, when the soundboard expands and the crown of the soundboard incre= ases, bridge will be pushed up. When the bridge is pushed up, the tension of= the strings is increased. And just as a rubber band will produce a higher p= itch when it is stretched tighter, the strings will increase in pitch when t= hey are stretched tighter by the pushed up bridge. And whenever the tension = of strings is changed, we perceive that a piano is out of tune. This effect on the soundboard is reversed when the humidity is very low, as = in the winter.  Even though the outside humidity during the winter mont= hs is about the same as during the summer, when moist cold air is heated, it= looses its moisture content. It is not unusual for a house to have a relati= ve humidity of less than 25% during the winter months. The greater the change in temperature, or humidity, the greater the effect o= n the soundboard. Since the temperature and humidity changes constantly, the= piano never really stays in tune. But since most homes now have air conditi= oning, and the humidity and temperature are controlled more, the changes are= not as dramatic as they used to be. Still, every time the temperature or th= e humidity changes, the piano goes out of tune. So the next time your piano goes out of tune shortly after the piano was tun= ed, think back about the changes in temperature and humidity. Most likely it= was the fault of the weather. But when you do hear the piano out of tune, t= he piano tuner should be called, because there is nothing worse than listeni= ng to an out of tune piano. </HTML>