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It's time for another tuning - last one was 6 months ago - and here the RH change between summer/winter is drastic. I already noticed that before, but this time after transferring the pitch variation of each key on a graph, it becomes even clearer. What I find interesting is how the variation in pitch is defined by the three stress bars or struts (orange lines) inside the piano and follows an almost linear pattern. For example, even though strings of keys 49 to 54 are longer than the ones of keys 55 to 59, they almost stay at the same pitch (red line = 0 cents) being on the left of the 2nd stress bar. But strings closest to the right of that same strut get the most pitch variation. One could think that if the struts influence the pitch variation of the strings because they are opposing/redistributing the stress as they provide stability for the frame, the maximum pitch variation should actually happen in the middle of each section (in this example, keys 41 to 43 and keys 63 to 65, as they are farther away from the struts). But instead, it follows a left/right pattern. Hence why I thought I would share this observation - kind of interesting. Maybe this varies from piano to piano.
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Am I reading your chart correctly, that some of the strings are getting sharper over time?
Poetry is rhythm
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Am I reading your chart correctly, that some of the strings are getting sharper over time? Yes. Here in the summer, RH goes way up, so if your house has no climate control, piano pitch goes up.
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Hi - what sort of piano, and size?
Alan from Queensland, Australia (and Clara - my Grotrian Concert & Allen Organ (CF-17a)).
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Most pianos are scaled so the elongation curve is reduced for the notes at the bottom of each top treble section compared to the notes at the top of the section. This means that for a given dimensional change the less elongated notes will change pitch more than the more elongated notes. (What I mean by elongation is how high a percent of the break strength the wire is placed at due to the speaking lengths.)
At the break between the overstrung section and the longest notes of the treble bridge, the same elongation thing is happening but the wound strings are elongated more due to the wrapping and thinner cores used.
I hope this is clear. If not, I can add more explanation and definitions.
In a seemingly infinite universe-infinite human creativity is-seemingly possible. According to NASA, 93% of the earth like planets possible in the known universe have yet to be formed. Contact: toneman1@me.com
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Hi Ed,
Yes it will be greatly appreciated if you can add more. Please feel free to elaborate when you have some time.
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Interesting graph! In my dum-dum lingo, am I correct that the pattern of pitch changes is not a result of the frame construction, but of the different string wire thicknesses (and therefore the different relative tensions the strings are under)? Strings which the piano scale design places farther from their respective breaking points will change in pitch more when the piano moves a given amount?
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If it has to do with the struts then my piano is of the hook No struts at all.
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Interesting graph! In my dum-dum lingo, am I correct that the pattern of pitch changes is not a result of the frame construction, but of the different string wire thicknesses (and therefore the different relative tensions the strings are under)? Strings which the piano scale design places farther from their respective breaking points will change in pitch more when the piano moves a given amount? Hi Ben, I think you are correct and that you reasoning is in agreement with what Ed was saying as well. I was trying to find a link with the frame stress bars on my grand piano, but it could definitely be wire thickness instead. Thanks for your reply.
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@Larry, can I borrow your glasses? I can't read what you wrote.
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It is the string length that matters for plain wire. Longer strings for a given pitch, change pitch, (for a given dimensional change), less than shorter string lengths. And the ratio between core wire diameter and wrap determines elongation for the wound strings.
What you are seeing is the effect curve of the bridge and the string spacing offsets caused by the struts on the bridge changing the rate at which the speaking lengths progress across the scale. Many piano are not scaled perfectly in regard to speaking length incremental change across the compass. Most bridges need to have more of a dogleg curve where they passe under the struts to enable placing the speaking lengths in a perfectly even progression from note to note so the amount of elongation the strings are placed under is even.
In a seemingly infinite universe-infinite human creativity is-seemingly possible. According to NASA, 93% of the earth like planets possible in the known universe have yet to be formed. Contact: toneman1@me.com
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If it has to do with the struts then my piano is of the hook No struts at all. Grotrian chose a different construction. The "star" back is made of many laminations, similar to their grand piano rim.
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Seasonality is really interesting in tuning. I don't notice it much on the piano, but on wood frame instruments like a harpsichord, it's a huge effect. Everytime it rains the harpsichord needs tuning. In the summer it is important to monitor the tuning or the tenor strings start breaking. Usually, the bass goes flat and the treble goes sharp on the Zuckerman. Part of this is due to the brass strings in the bass.
Seiler 206, Chickering 145, Estey 2 manual reed organ, Fudge clavichord, Zuckerman single harpsichord, Technics P-30, Roland RD-100.
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If it has to do with the struts then my piano is of the hook No struts at all. Grotrian chose a different construction. The "star" back is made of many laminations, similar to their grand piano rim. I had a YAMAHA UX (1979) - which had a similar X Back bracing. It kept it's tune amazingly well.
Alan from Queensland, Australia (and Clara - my Grotrian Concert & Allen Organ (CF-17a)).
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It is the string length that matters for plain wire. Longer strings for a given pitch, change pitch, (for a given dimensional change), less than shorter string lengths. And the ratio between core wire diameter and wrap determines elongation for the wound strings.
What you are seeing is the effect curve of the bridge and the string spacing offsets caused by the struts on the bridge changing the rate at which the speaking lengths progress across the scale. Many piano are not scaled perfectly in regard to speaking length incremental change across the compass. Most bridges need to have more of a dogleg curve where they passe under the struts to enable placing the speaking lengths in a perfectly even progression from note to note so the amount of elongation the strings are placed under is even. Would it make any difference in how large or small the piano was - or do large/small pianos both have the same effect?
Alan from Queensland, Australia (and Clara - my Grotrian Concert & Allen Organ (CF-17a)).
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@Sam, looks great. I wonder though how Schimmel has worked around the usage of struts. They have been doing this since 1930 so it makes me wonder why no other builder has adopted the idea.
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Hello Bosendorff, What are you plotting on the y-axis? It looks like it may be in cents but is it the deviation of the first partial as observed by a line spectrum from the fundamental as defined by equal temperament? If not, then how are you defining pitch? Alternatively, is it the deviation in cents of the first partial's frequency as compared to the last tuning? Thanks.
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I may have an answer.
May I first have the; 1 scale for the Y axis 2 speaking lengths for a few notes before and after the break 3 wire diameter
I have written my intended answer down and I'll post it after verifying a couple of things.
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Hello Bosendorff, What are you plotting on the y-axis? It looks like it may be in cents but is it the deviation of the first partial as observed by a line spectrum from the fundamental as defined by equal temperament? If not, then how are you defining pitch? Alternatively, is it the deviation in cents of the first partial's frequency as compared to the last tuning? Thanks. Hi Dave, The y-axis shows the variation in cents, with red line = 0 and each horizontal line = 3 cents. Temperament and partials don't really matter as I'm using the same TuneLab file for comparison since last tuning. So for example, D30 is now 9 cents sharp compared to 6 months ago (remember, here we have drastic RH changes - and in the summer piano goes up in pitch), but G#72 went flat about 3 cents. I may have an answer.
May I first have the; 1 scale for the Y axis 2 speaking lengths for a few notes before and after the break 3 wire diameter
I have written my intended answer down and I'll post it after verifying a couple of things. Hi Larry, The speaking lengths all follow a smooth progression : Keys 75 = 9.5 cm, 74 = 10 cm and 73 = 10.5 cm (right of last stress bar), then keys 72 (left of last strut) = 11 cm, 71 = 11.8 cm and 70 = 12.5 cm. Then to the right of the "middle" stress bar come keys 57 = 24.5 cm, 56 = 26 cm and 55 = 27.5 cm and to its left keys 54 = 30 cm, 53 = 31.5 cm and 52 = about 33.3 cm. About string gauge, I don't have a micrometer so I can't tell. Thanks in advance for your next reply. ------------- The exact values are not so important - what I find remarkable is the obvious break in pitch variation linearity near the two rightmost frame struts. Even though I agree with what Ed and Ben said here - and that string gauge and elongation vs break strength have an important impact on pitch variation, and also the bridge curve and spacing around them, the struts seem to also play a role in redistributing the stress and defining the pitch variation between tunings, especially since a few keys on my piano end up going flat instead of responding like all others to the RH increase.
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