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Sometimes I would get calls from customers that went something like this – “I am playing a song on my piano and some of the notes sound like I am playing two or three notes at once. Why is it doing that?” As I would explain to them, this is something I could not diagnose over the phone and usually I would schedule a service call. There are just a few main causes for this effect, and the only way I could be sure which one is the culprit is to look.
The first possibility I would check is if the hammer is traveling correctly. If the screw that holds the hammer flange in place has worked loose, or the flange has cracked, or the glue seal at either end of the hammer shank (the stick that the hammer sits on) has broken loose, then the hammer might not be staying straight as it travels from rest position to the string, and it could easily be striking both one of the strings in its unison and one or more of the strings in the next unison. In this case it would be a matter of determining which repair was needed and making it. This type of problem tends to most commonly in older pianos and pianos that have been moved long distances.
The second possibility is based on the concept of the unison. On the piano, each note in at least the upper half of the range of the keyboard will have three strings. In most cases some notes just below the notes with three strings will have two strings. Only the lowest ranges will have only one string. (NOTE: Where each of these breaks takes place will vary somewhat from brand to brand, and is a major component of the scale design.) I said all of that just to say this – each of those groups of 1-3 strings is called a unison, and when the piano is correctly tuned all of the strings in each unison will be tuned identically, so that each unison will sound like one note. When one or more of the strings goes out of tune you will get the multiple-note sound. Fortunately, usually all that is required here is to re-tune the unison. In some cases the tuning pin might not be seating correctly because of the advanced age of the piano, and the technician will need to either drive the pin in a little bit to seat it better, or remove the pin and re-install it with a tuning pin bushing to make it tighter.
There is a third possibility. Sometimes a piano would need tuning but the owners had not noticed it because the shift in the tuning had been sufficiently gradual that their hearing had compensated for it (“I knew it wasn’t quite as good as right after it was tuned, but it still sounded okay…”) but then one or more unisons had gone far enough out that they noticed them – just not the rest of the piano. Usually in these cases the owner would not be able to remember when the piano was last tuned, but once the piano was tuned they could definitely hear the improvement. You get the oil changed in your car about every three months. Why not make a point to get your piano tuned at least every other time you change your oil?
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