Rebuilding pianos and creating music are my passion. Living in Northern Wisconsin gives me the ability to enjoy the beauty of the area while maintaining my career.
Tuning a piano is like tuning a guitar except there are over two hundred strings and each wire is pulled to a tension of 150 to 300 pounds. A guitar string is about 15 pounds of tension. The average piano carries about 35,000 pounds of tension. When you tighten up the strings on a piano, the entire piano changes shape. On a poorly made piano the frame might twist by a quarter-inch.
A tuner pulls the string tighter to raise the pitch and loosens it for a lower pitch. When two strings are sounded together they create a "beat" or an even wavering of tone described as a "waw-waw" sound. Certain pairs of notes create a clear beat (such as the tenth, or a low C with an E ten notes above it). The tuner is generally setting the speed of the beats and does not need to think sharp or flat. You might have heard a "waw-waw" beat when the two engines of a boat have a slightly different RPM. Locomotives can produce the same effect.
The sound produced by a steel string has some strange properties and this is what makes tuning interesting. Different pianos will need different tuning, especially in the lower half (the left half). Here drastic compromises need to be made in the design and the tuner will need to find the least offensive solution.
Surprisingly the hardest part for a good tuner is getting those steel wires to move to the right place and to make them stay. The wire goes around a bend here and there and develops a kink. You pull the wire tighter and tighter and nothing happens until you here a 'ping' as the kink moves off its spot and the pitch jumps well above where it should be. A slight sideward pressure on the tuning pin can encourage the kink to move more easily but some pianos are almost untunable because of this.
Moving the tuning pin may be the most complicated part of tuning. The tuning pin is roughly two and a half inches long and a quarter inch in diameter. It is driven into a hardwood plank and is turned with a tuning hammer. A great deal of strength is needed to turn this pin and it twists as you move it. (More happens than just twisting but the image is a good starting point.) If you raise the pitch and just let go of the tuning hammer the pitch may drop back down. If you hit the note very hard it will surely go out of tune as the pin untwists. A good tuner knows how to 'set' the pins. Generally, you would bring the note slightly above pitch and twist the pin downwards. Now the pin is 'sprung' against the tension on the string and is very stable. This is why a poor tuning may sound good today but go out of tune in a week.
Another difficulty is that tuning a note may change the notes around it. If you raise the pitch of one string, the notes around it will drop slightly. A rule of thumb is to raise the pitch above where it should be by half the amount it was below pitch and it ends up roughly correct. However, certain areas of the piano react differently and different pianos will react in different ways.
What a client gets from my twenty five years of experience is speed and stability. In an hour and a half I can take a horribly out of tune piano and bring it up to the correct tune. One fifteen minute tuning, then a one hour tuning and then fifteen minutes to correct any remaining problems. I don't brag about the accuracy of my tuning simply because only another tuner would be able to detect the minute differences between two good tunings.
As a guitar needs new strings once or twice a year, a piano needs new strings once or twice a century. Your piano might need a restringing if the strings start to break, or they sound dead, or the tuning pins (see thoughts on tuning) get loose and won't keep the string up to pitch.
If the strings get replaced the tuning pins and a part called the pinblock are replaced also. Once this is done the piano will be fine for another century.
Generally, some felts are replaced and the soundboard and harp (the big gold frame) are refinished. Rebuilding may also include replacing other parts that are worn out, such as the hammers. Hammers are blocks of felt that hit the string when a note is played. Changing the hammers may change the piano drastically.
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