Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Why would a piano go sharp?

I can see why tension in strings would pull the pins flat; but what would account for natural tension increase? Tension is energy. Doesn't that energy gradually disperse?

Not sure if my answer is addressing your question from the perspective you wish it to, but I will take a stab at it. First of all, a significant shift in temperature will change pitch. Hot stage lights directly over an open grand will cause the strings to go flat. It has to do with elongation due to coefficient of thermal expansion...the steel will expand about 6 microns for every degree F the temperature increase, per inch. Strangely enough, nylon guitar strings do exactly the opposite (they go sharp with heat from finger or friction). The difference is due to the nylon's Van der Waals (VdW) bonds and crystaline structure which forces more radial expansion rther than elongation in the string (among other reasons also).

Another reason the string will go up in tension "naturally" is from the soundboard rising or bowing out more from higher humidity levels and moisture absorbtion. The strings ride over the bridge on an angle with downbearing and this will increase as the soundboard rises. We typically see the tension and pitch go up in the summer, and down in the winter...all in respect to the changing relative humidity. Its not unusual for a piano to shift 10 or 20 cents between the seasons. The shift is not equal over the whole keyboard, so the piano will not stay in tune with itself over all from this type of shift.

I like your kind of answer. Fascinating. I think, 'I wish I had taken physics in school,' but then again, if I had I wouldn't have valued it at the time. Life.

Ok, next question:

So, the 'cent' measuring system was started by Helmholtz, right? A nice and clean division of the octave. But how can other temperaments measured in cents? Can you explain the math of why a 'just' major third is 386.31 cents? How do you get 386.31 from 5/4?

Thanks!

It has to do with elongation due to coefficient of thermal expansion...the steel will expand about 6 microns for every degree F the temperature increase, per inch.

So, temperature effects metal as well as wood? (Please excuse my naiveté!)

Yes temperature does effect the wire. In fact we had a member here a few years ago who was developing a self tuning piano which operated on this principle. The strings would be individually heated to get to a predefined pitch, the piano of course would be sitting sharp before the self tuning starts. Each string had some kind of optical reader on it to measure the frequency and the piano would set itself to an original master tuning done on it within a minute or so. He probably ran into some issues since I haven't heard much about it since....it sounded like a good concept though.

I will let someone else explain the cents and how it relates to temperaments/tunings. If its not ET on a piano, I use a differnt criteria for the tuning assessment....crap/crappier/crappiest.

Yep. For the OP here is a photo album I have posted previously about humidity changes to the sounding board. Text in the tray on the right of each photo.


Humidity and the sounding board

when high treble raise it is because the tuning pins have been "set" too strong, as it happen easily when one tune a newly stringed piano.

With a new/recent block, the pin can be left with too much power, and the pitch raise a few minutes later.

about environmental reasons, we have a 439- 444Hz difference for pianos tuned at a 442Hz standard, between winter/heat and summer. (this occure on the most central octaves, progressively less toward basses and treble)

School pianos I find at 443 and more in september, so all the tunings are done taking in account the way they will evolve with the next season.

there is more stretch in winter ? no problem, I will not lower the treble to match, not much anyway.

As a professional tuner and technician, sometimes the math of tuning exceeds the necessary facility needed to excel at the craft. I'm saying this as an engineer as well.

It has some interesting qualities, this question about just thirds in cents, but from a purely performance point of view, there is no benefit to knowing the answer, IMHO.

Are you a piano tuning student? Technician? Pianist?

Hello Mark,

I am a pianist, and have recently aquired a desire to learn to tune. I will begin apprenticing with someone. I am still going through the basic - pre-basics, actually: reading, listening, talking to people.

I'm still a tuning virgin. I took my first stab tuning a few strings last night. I'm a purist by nature, so when I went to tune some fifths and thrids - I have no system yet, just experimenting - I was appalled by what I heard. Being a student of music in general, I'm embarassed not to have known what tuing really is until now. I always just took it for granted: in tune, not in tune. I see now, there's no such thing as 'in tune.'

I tuned an A3;
Then E: nice 5th;
Then D from A: nice 4th;
Then G: nice 5th;
Then a B from E: nice 4th;
Then an F#: nice 5th;
Then a C# from A: very, very nice 3rd;
Then listened to the 3 parallel 5ths in a row. Wow! How clean, how pure, how magical, how healing and disturbing at the same time - disturbing because my brain had never been accustomed to so much energy before. It's like that line from 'The Matrix' where Neo 'wakes up' in the real world and says, "My eyes, they hurt," and Morphius answers, "That's because you've never used them before."

These tones - they really sing.

I used to play violin when I was young, so I know what a nice 5th sounds like - but never on the piano. Interesting.

Anyway, enough of the essoteric. I admired the 5ths for a while before I tried some of the other combinations. What an A major triad! (I don't remember what G-B-D was like. I didn't tune the B from G, so it must have been a comprimise, but I guess it didn't make an impression.) Then came the horror: A-F#. Amazing!

I heard about this stuff in books; treatises go on and on, etc. But, what I felt like was, 'Why has no one ever told me about this?' What made the difference was that I had done it. I was responsible for these intervals and what they sounded like. I had created something absolutely pure, something a piano never gets to have for itself. And, I had created a monster. The power was in my hands . . . and, of course, the resonsibility comes: to learn how to tune responsibly. Not just in terms of temperment, but also piano care.

It's an exciting beginning.

I'm not a DIYer, but I can't wait around for someone to tell me what to do. I'm a difficult student because I never do things without knowing why I'm doing it.

If I'm being asked (by ET) to take a 3rd atrociously sharp, I want to know why, and how much, and what creative thiking is behind that amount.

Another thing happened:
I tuned a 3rd, by ear (that is, a just 3rd,) and then checked my KORG-CA40 tuner to see what it was like. I was very surprised. I had written down Pythagorean's calculations for intervals, in cents, and was expecting to get a sharp 3rd. It was way flat! I later understood the difference.

Pythagoras: 407.82
ET: 400
Just: 386.31

Of course, one doesn't need to know these figures to tune a piano, just as I don't need to measure a doorway frame to know if I can walk through it without getting stuck. All these tuning systems come from people who have thought sincerely about the subject of music - people who care, and many of them ture masters. Studying all their mathematically tedious logics is my way of being influenced by a master, just as playing a Beethoven score is a way of taking a composition lesson from a guinius.

I don't make a good DIYer becasue of my affection for theory.

Nice to meet you, Mark. If you've read my whole spiel here, than I hope it's not an off-putting introduction. I'm here to learn.

One of the other guys on these forums has this quote:
"In theory, theory and practice are the same thing; in pracice, they're not."

Michael Parks

What a nice writing !

Good luck with the art of tuning.

I had a question : did you listen to one string intervals? Unison make a difference in the sense they enlarge the Grey zone, justness wise.

Best regards

No, I believe they were just center string intervals. I had some trouble with pin setting, so by the time I was trying to unify the string triplets, I was going more and beyond my skill.

I see why pin setting takes practice - it's a 'feeling,' right?