I try to keep the complexity (and length of explanation) to a minimum when I talk to clients about this:
Piano strings are under very high tension, which increases the stiffness of the strings. This distorts the higher overtones such that the treble of the piano needs to be tuned sharp and the bass flat to make the piano sound in-tune with itself
This explanation has several benefits:
a) it explains why pianos are so different than other musical instruments, which is usually where people's confusion starts
b) most people have heard of overtones so I don't need to explain anything about it
c) it describes the readings that their chromatic tuners would show them
d) it is very short and satisfies most clients without their eyes glazing over
Of course, if the client has more questions I am very happy to explain how it all works in more detail, but for most people, this is all they want to know.
Oh, and I already know that I am going to piano tuner hell for telling clients that the overtones are distorted instead of saying that the partials are distorted and then having to explain to the client the difference between an overtone and a partial :)
------------------------------
Peter Stevenson RPT
P.S. Piano Service
Prince George BC
250-562-5358
ps@pspianoservice.com------------------------------
Original Message:
Sent: 01-27-2017 12:45
From: Floyd Gadd
Subject: Explaing inharmonicity to customers
I tried an experiment this morning. Using Tunelab, I set up a new file with no inharmonicity readings, so that when I chose a note and scrolled through the partials, they were all perfect multiples. I then took multiple measurements of A2, starting with the fundamental, and scrolling up to about the 12 partial. The fundamental could be seen as being somewhat below 110 cps, and the partials could be seen getting progressively sharper as higher partials were measured.
Maybe another simple argument for the customer would involve demonstrating the presence of the higher partials in the lower note using the ghosting technique, demonstrating the "stretch" that occurs in the partials of the single note, and explaining that the higher A's need to find some agreement with the partials of the lower note, not with some mathematical ideal.
I don't have a guitar tuner with me, but it would be interesting to see measurements of the various partials of a single note, again using ghosting to excite the partials we wanted to measure.
------------------------------
Floyd Gadd
Regina SK
306-721-9699
------------------------------
Original Message:
Sent: 01-27-2017 12:17
From: Geoff Sykes
Subject: Explaing inharmonicity to customers
Vincent --
I have been using a similar discussion with my customers but was using the thickness of the string and the fact that the termination point is not finite as the reason for inharmonicity. In other words, the termination point is a curve, not a hinge. Same thing with partials. I like your wood cut example a lot more. Totally removes the science from the subject and turns it into easily understood logic. Thanks for simplifying.
------------------------------
Geoff Sykes, RPT
Los Angeles CA
------------------------------
Original Message:
Sent: 01-27-2017 09:06
From: Vincent Chambers
Subject: Explaing inharmonicity to customers
Note: I am not an engineer or piano designer. My degree is in music, but I explain this all the time, so either my clients are super bright, are lying to me to be kind as I stand there wearing a foil hat, or my explanation sort of makes sense. Slightly.
I explain it like this:
Suppose you have a wire which is 1 meter in length, which is 100cm (we don't use the metric system here in the US commonly, but the math is easier).
That wire is vibrating 100 times per second, which we call 100hz (I the play a note in the range of 100 like A2).
As crazy as it sounds, the half length of that wire is vibrating as well, in two equal lengths. This produces a pitch which is double the value of the fundamental pitch, which is an octave.
Now play a note while touching the wire at half length to demonstrate harmonic to the client.
This division or point has no mathematical value, which is impossible, right?
This point must have some value, which varies with the weight and tension of the string. This half-length pitch should be 200hz or two hundred cycles per second, and the half length of the wire should be 50cm, right? Approving nod....hopefully.
Now, imagine cutting a piece of wood - a 2x4 - in half. If it started out as 100cm, would the two halves be equal? Of course not, since the width of the saw blade would have to be subtracted. If the saw blade is 4mm, then each segment would be 49.8cm, and this shorter length will vibrate slightly sharp of 200hz. This discrepancy, or out of tune-ness, is called inharmonicicy. I also explain that a short piece of wood has less flexibility than a long piece - which everyone seems to understand. Hence longer string = lower inharmonicity.
I then explain that there are many subdivisions of the string, and the each segment is more out of tune mathematically than the previous division simply because there are more "cuts" to the wire, and send them off to the source of all things good and true - Wikipedia - so that they may mentally remove my foil hat and reclassify me as Not Quite Insane.
I do this about 5-6 times per week, and have several apprentices I'm in the process of explaingin this to. The thing is, intellectually it's pretty straight forward, but man, when you start trying to teach an actual musician to listen to the piano this way, you realize how little headway you've actually made.
My ultimate goal is to explain this in 2 minutes, satisfy their curiosity, redirect them towards getting me a cup of coffee, and maintain billable hours. Perhaps a simple brochure on how this subject would be worthwhile.
Wow, I really should stay away from the internet when I can't sleep.
------------------------------
Vincent Chambers
Chico CA
530-924-4469
------------------------------