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.
An octave on a piano is the distance between two notes that have the same letter name.
They are separated by eight white notes, if you include the first and last note. If the lower note vibrates 200 times a second, the note an octave higher will vibrate twice that, or 400 times a second.
If they are tuned perfectly, no beat will be made. However, the piano insists that all octaves be stretched a little. This is where tuners have some latitude. A piano tuned with perfect octaves will sound dull and flat. If the octaves are stretched a lot the piano sounds bright and pleasant, although certain pairs of notes will begin to beat too fast and sound bad. Personally, I like more stretch, especially the top two octaves and the bottom octave. It seems a classical pianist will prefer this as the top has presence and the bottom has a bigger sound from the extra beats. Jazz players seem to prefer less stretch, as if they're more focused on the beats produced by complex chords.
Different pianos need different stretches. If the piano is a larger, better piano, the stretch may be small and very regular because the tone is very pure. Cheap pianos, especially very small ones, are so confused that a tuner does not know what to do. Ironically, a really cheap piano will often sound fine from a haphazard tuning. The beats are so confused that the ear quits using them as a reference. Certain small pianos will, upon playing the tenth interval, have not one, but two beats. One beats slowly and tells you to raise the pitch and the other beats fast and tells you to lower the pitch.
A really good tuning will have an even "progression of tenths." If you play each tenth in succession (C to E, C sharp to F, D to F sharp) the speed of the beat will gradually increase as you go up the piano keyboard. I focus on the progression while tuning and this could be considered my individual style.
There are a few hiccups in any progression. These are due to the "break" between the tenor and bass strings and the change from two strings to one string per note near the left end of the piano. These transitions require a big change in the string tension and this always interferes with tuning.
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.
The hammer is a block of felt stretched over a wooden core. When a key is pressed the hammer flies up and hits the string, making it ring. A hammer for the high notes may be one quarter of an inch thick and about two inches long. A bass hammer will be about one and one half inches thick.
There has been a great change in hammer making over the last forty years. This topic leads the list of piano part descriptions because I have a very strong belief that they "don't make them like they used to". There are some pianos today that have superb hammers, but they are few and far between and still do not work like the old ones. If you have knowledge of felt or the felting process and can shed some light on this, please email me.
The felt is glued on the wood core under tremendous pressure. The machine that does this costs millions of dollars. The traditional view is that this stretched felt is bouncy or elastic and the hammer rebounds from the string quickly, letting it ring. A golf ball or baseball is another example of this dynamic. A perfectly hard ball would not work at all. Yet, the machines get old and weak, the company puts off the costly replacement, and there is pressure to turn out more sets per week. Hammers made today have no tension and a chemical hardener is added to make them hard enough.
For those of you who know about felt, here are two more characteristics. Let's say you have an old and a new hammer that weigh the same - the old hammer will be much larger. When you stick a needle into old felt, you feel a structure. New felt feels dense and waxy. Older felt is yellowish - perhaps it is not bleached the same way. It seems that kinky hair would felt with greater elasticity and new felt is rather straight.
Hammers are blocks of felt that hit the strings to make them sound. Sometimes they need to be replaced. The felts get cut by the strings after years of use and a technician will file the cuts out of the felt. After a while there will not be enough felt left and the touch of the keyboard will be too light and uneven. Often old hammers will pack down so hard that the tone they make will be harsh. Yet of all the parts that can be replaced, the hammers may change the entire piano from the player's point of view.
New hammers are not made the same way as the old ones and vary in quality from decade to decade and batch to batch. Hammers were especially bad in the 1980's. The thinking was to make a heavy hammer in order for it to last longer. Unfortunately, a slight increase in hammer weight makes the piano practically unplayable. Also, the felt was too soft. There were many Steinway concert grands back then that got new hammers and the owners were devastated. They were told that the hammers needed to be "broken in".
Good hammers are available today and they're weight can be carefully chosen, however they still need a great deal of careful work to get great results.