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Hi everyone! I have a Kawai digital piano and it exhibits the following behavior: when I silently press C then play C# or B, I can clearly hear C resonating as well.
http://www.youtube.com/watch?v=xJreG6BFmX8&feature=youtu.be

I've written an e-mail to Kawai describing the issue and they replied this is normal behavior. Which is weird, because I have C# or B don't have any harmonics in common with C verified up until the 10th harmonic.
https://docs.google.com/spreadsheet/ccc?key=0AmAewoLG-n9AdHROVVJSSjhPN0tLYW5XdDNtN0o5ZFE

I don't have access to an acoustic other than my teacher's piano, so I wanted to know if this behavior is indeed normal or if only Kawai pianos display it. If so, then what is the reason that C also vibrates?

Thank you.

Yes quite normal .... any acoustic piano would do the same! A broken damper in that area would allow all sorts of harmonics to vibrate in sympathy, and what you're doing is inducing the same effect on your digital.

It is not normal. I can hear the C's fundamental clearly and that should not be. There should only be a wash of various higher overtones of C maybe depending on the other note struck. Does it do the same thing on other notes?

This certainly is not wanted, nor does it serve any harmonic purpose. As far as it being "normal" for this model, you should first determine if it exibits the same thing on other notes also...or is it just this C note. Secondly, try and find out if somebody elses Kawai (same model) does the same thing. There may be some voltage bleed through on a circuit board where two parallel crcuits are not properly insulated from each other. There is no sympathetic vibration going on since this DP uses sampled sound...no physical strings present.

I'll just shut up then Bogs ..... Clearly I and Kawaii are talking a load of rubbish !

Johnkie, if it's a bit of consolation, I tried to say the same in another thread on the digital piano forum here on PW, with similar success. Goes to show how well people know the instruments they are working with...

Perhaps this is best asked in the digital forum? As this is the acoustic piano forum?

As for acoustic pianos, if properly tuned, John is right. If you hold down C-4, then play E-4, G-4, C-5 etc., all the way up, then every single one of those notes will sound through on that one C-4 which is not being shut off by the damper because you are holding it down. That IS normal. It should do it on any key that you choose to play on, however if you play C-4 and make then play D-4, some sound may come through but not like it would if you played notes related to C-4 and probably, not nearly as much so.

I do have to wonder, why in the heck are you doing that in the first place????

I have no idea how it would be on a digital piano because piano tuners (most of us anyway) do not work on these things.

When you write to a company inquiring about their product, there is no guarantee that a qualified person replies with a decent answer. In fact, most companies have a series of defenses you need to wade through to actually get a decent answer from the proper person who knows what they are talking about.

The first line of these defenses are people (often secrataries)known as deflectors. They typically know nothing about the product and throw "canned" form letters or answers back to the inquirer to deflect further inquiries. They don't want to bog down their highest paid employees with customer inquiries. Successive and repeated inquiries will often find their way to the design engineer(s) and quality control folks who have the ability and resources get to the bottom of things and come up with a decent explanation.
A first time call or written complaint/request rarely gets to these people unless its a huge safety or liability issue.

I am not an electronics wizard by any means, but can't subscribe to "Electronic bleed through" on a digi piano, especially when Kawaii techs have already been asked if this manifestation is a fault. Generally speaking faulty electronic components result in either something not playing at all, or an uncontrollable cipher

My Guess .... and only a pure guess .... is that the guys at Kawaii have researched the properties of acoustic pianos and incorporated this effect to add realism. It is perhaps a little over exaggerated, but I personally do not consider it to be a fault, more part of Kawaiis intended design.

John: Would you really expect to hear the fundamental of C4 if you held the key and pressed C#4 or B3? That is what the video shows, and it is really odd behaviour. I think you might have misunderstood the original post to be honest, or maybe not watched the video?

Don't accept Kawai's original answer, Bogs. Pianos shouldn't do that, nor should digital pianos.

Edit: Never make an assertion without testing it yourself. My piano does indeed exhibit this behaviour. Ignore what I said!

But they do. Please, people, sit down at your pianos and try for yourself.



Indeed. And that realism makes sense since the situation is not as rarely occuring as it might seem - after all you get these kinds of 'neighbouring resonances' whenever you play notes with the damper pedal down, or in other situations when you hold a chord with one hand and play something in between with the other. Etc.

Johnkie +1
My acoustic behaves similar.

*shuts up*

If you hold down C on an accoustic piano (to lift off the damper) and play the B or C# to either side of it to ghost a tone, you will not hear the fundamental C ring out.
There may be some incredibly soft very high order partials excited but nothing even close to what your hearing on the DP. This is not an accoustic phenomenom which I think someone would diliberately want to mimic with a DP (exciting a non related harmonic).

I talked with my brother who is an electrical engineer and he confirmed my original suspicians of "bleed through" not being correct on a digital piano (as another poster mentioned). It could easily occur on analogue systems, hi fi's ect...
His suspicians are that its crappy software, if it indeed is not intended to be there. A rogue line of programming or something like that.

So ask the technicians here...
Is the fundamental pitch of C something you want to hear when playing its two neighbouring notes to either side?

Accoustic pianos don't audibly display this if you try to ghost the tone using the immediate neighbouring keys. Wouter, I'm not sure what your hearing, but its not happening on any of the accoustic pianos I just checked it on. Theory supports this since B and C# do not contain the fundamental frequency of C between them.

Emmery, I find this hard to believe.

Maurus, in order to excite sympathetic vibration on a string the resonant frequency used to do it must match. What frequency in B or C# can excite the fundamental of C which is beside it? No such frequency exists in either of those notes. The closest note below C, to excite its fundamental frequency is the C note, one octave below it...this is a fact.

Thank you everyone for their responses.

Just to make matters clear - what you heard on the video is what happens no matter what key you have depressed, as long as you plan a note a semitone higher/lower, you can hear the depressed key resonating.

The Kawai support guy told me he tested this behavior on Kawai GE-30 and the result is the same. Maurus, who also has a Kawai, said his acoustic piano also exhibits this behavior. I see others here claim the same.

But from the theoretical(physics) point of view, C and C#/B don't share any harmonics [as per the google docs spreadsheet]. It's normal for G and F and E, etc to excite the C strings, but not C# nor B.

Now the question is, are Kawai pianos 'special' and exhibit this behavior? And if so, what is the reason? Someone said the hammer may hit the strings next to it, and thus set it in motion [so no sympathetic resonance involved and thus no violation of the physics laws regarding vibrating strings]. This theory is also supported by the fact that if I silently press C4 on the Kawai digital, C#4 and B3 excite the C4, but neither C#3 nor B2 (also C#5/B4) do.

Any thoughts?

Bogs, this is not related to brand at all. Just carefully check any acoustic piano of your choice.

And, as an aside on the physics: A damped vibrating string (all strings in a piano are in fact slightly damped!) does indeed respond to very close neighbouring frequencies.

Maybe Kawai has an algorithm that simulates partials and harmonic overtone so as to enhance the tone and mimic an acoustic. Possible, right?

As others correctly mentioned, this is an acoustic piano forum, and many of us are not digital piano techs.

Well Maurus...

All strings are not damped in a piano. Typically the dampers stop at a point in the treble where strings tend not to have as much sustain as lower notes. I have never seen a piano with dampers going up to C8. What is it that you mean by "slightly damped"? Short sustain is not dampening. Natural decay of a sound on a string is not dampening either.

Secondly, if you notice, I refrain from using generic terms such as "respond" when in fact I refer to a property of a string picking up on another strings vibration as "sympathetic" resonance or vibration. The entire bridge and soundboard of the piano vibrates from one note playing. Many other strings are connected to the same bridge (segment) and vibrate at the bridge connection because of their physical connection. Only the undamped strings will pick up on this connection and only if they share the same frequencies and partials of the excitation frequency. Properly dampened strings will not produce audible sympathetic vibrations of this nature....thats why they are damped.

They do not however, all sympathetically vibrate at like pitches unless they share the fundamental frequency or partial ladder. Hold down C5 and play C4 (staccato)and you will clearly hear the fundamental of C5 excited by C4's first partial (along with numerous other coincidental partials farther up the ladder).
If you do the reverse however and hold down C4 and strike C5...you will hear C4's first partial excited...not its fundamental...C5 does not have the coincidental frequency to do so...its lowest frequency is twice that of C4's lowest frequency.

Now using unrelated notes such as B or c# to excite the fundamental frequency of C that lies next to it, will simply not work. THEY SHARE NO COMMON FREQUENCY WITH C'S FUNDAMENTAL. You may hear a very faint busy mix of super high partials way up the ladder, if they happen to be coincidental, but definately nothing clear or concise and DEFINATELY NOT THE FUNDAMENTAL FREQUENCY OF C AS HEARD IN THE DP.