As your Piano Tuner Wilmington DE , I am occasionally asked about “Expanded Octave Tuning.” The following is an explanation that may help with understanding the complexity of tuning a piano.
“Expanded Octave Tuning” refers to the fact that octaves on a piano are never tuned perfect. They are always tuned wide by varying amounts. Some explanation of the physics of wave motion will help explain this.
When a string vibrates, it has a very complex motion. You may be familiar with the shape of a sine wave. It looks a little like the letter “N” with the angles rounded out. That one movement of a piano string is called the “fundamental” or the “first partial.” All along that string, there are additional smaller waves that result in higher pitches called “overtones” or “partials.” These are not random, since they all need to stop vibrating at the end points of the string. That is where the term “partial” comes from. Essentially, the string will be divided in 2,3,4,5,6, and 7 waves all happening at the same time. The pitches that result are perceived by the ear as the quality of sound. Each of us can tell the difference between a tone made by an oboe and one made by a piano, even if both are the same pitch. The way we tell which sound is which is by our perception of the overtone pattern. If the sound of each of those instruments is recorded and has the overtones electronically removed, they sound exactly alike.
The second partial is half the original wavelength, and is perceived as the next higher octave. If we are to tune an octave on a piano then, we would align the second partial of the lower note with the first partial of the higher note. That can be done on a harpsichord or an organ, but a piano is different.
The difference in a piano will take more explanation, which will be done in our next post. If you have any questions about pianos or piano tuning, repairs, or piano maintenance, please give us a call. We are your Wilmington DE piano tuning experts. Along with Delaware piano tuning services, we serve the areas of Philadelphia, Eastern Shore MD and Southern NJ.