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I have a Casio CDP S150, which allows the capability of layering tones. I noticed something strange happens when I layer the different piano tones on each other (standard piano tone+mellow piano tone, or any other combination). If I play 16 keys keeping the sustain pedal on, the 17th key onwards the sound comes out muffled. Demo video can be found here

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The Casio support team came up with different suggestions as to why this would happen, but none of them sound satisfactory to me for the reasons mentioned below:

  1. Possible reason: the piano has a limited 64 note polyphony, and so the piano starts dropping notes.
  • I checked the issue after enabling metronome (which should consume some of the polyphony). The issue still occurs after 16 keys.
  1. Possible reason: the layered piano tone is played after a small delay from the first tone, and this causes overtone cancellation.
  • If this were the case then the effect should have started from the get go, rather than happening after 16 keys. This does not seem like a reasonable explanation either.
  1. Possible reason: There is some sort of a "flanging" happening due to the layered piano tone.
  • It is unclear why this should only happen with the piano tones and not any other layered tones. When I layer harpsichord over the harpsichord, there is no such effect which occurs. Thus this issue is very specific to the piano tone library.

I checked using the spectrogram app, that the fundamental frequency gets damped compared to the overtone when the piano sounds weird.

This problem is likely not just related to only CDP S150, but to all other Casio models.

Can somebody explain what could be going on and if you own a casio (or other) digital piano but with a different model can you confirm that you also see a similar issue?

SuMo
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    Generating a tick is nothing like generating a voice, and might even be taken care of by a different hardware: imo the metronome should not consume some polyphony. – Tom Feb 06 '22 at 09:06
  • I guess this is why Casio has this reputation of toy keyboard even if they're trying to make serious instruments. I think this would require someone with inside knowledge for real answer but I can speculate that there's a specific algorithm for piano tones and a different one for other sounds, and the piano algorithm has this bug. It could go unnoticed because layering two piano tones and playing lots of notes with pedal pressed is not that common. – ojs Feb 06 '22 at 10:11
  • Further speculation: It could be that the piano tones are made up of two parts, so two layered piano tones and 16 notes would use the 64 polyphony slots. At that point the bug would kick in and instead of dropping already ringing notes, it would drop the part of new notes that contains the fundamental and play only the part with overtones. – ojs Feb 06 '22 at 10:17
  • @tom I also checked with a single piano tone to see if the issue repeats after 32 notes just to test out the polyphony issue. But that does not happen either.

    It does seem like a bug to me too.

     – SuMo Feb 06 '22 at 10:24
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    Something is broken with note stealing in this case, they didn't take this exact combination of settings into account and didn't test for it, or maybe tested and noticed but thought it's an edge-case they don't have to care about. You won't be able to fix it, and Casio most probably won't fix it for you. Making a software change is expensive, people need to spend work hours on it. There are worse bugs in Casio keyboards. Return for refund or just don't play with layered acoustic tones. Why would anyone want a layered acoustic piano anyway? (I'd get bored with the sound pretty fast) – piiperi Reinstate Monica Feb 06 '22 at 10:25
  • @ojs I agree that this seems more like a bug, I am not very happy with Casio support either. I have been very patient with them but their focus is more on saying "there is no manufacturing problem", rather than understanding the issue and at least trying to address it. – SuMo Feb 06 '22 at 10:27
  • "Why would one want a layered acoustic piano anyway" exactly. This is not even the worst thing that could happen. My old Yamaha digital piano had sample sets taken from different real pianos, and because they had different stretch tuning curve layering two piano sounds would give all kind of flanger or saloon piano effects. – ojs Feb 06 '22 at 10:28
  • I would agree that it's not a manufacturing problem, it's working just as designed and they don't consider it a problem. – ojs Feb 06 '22 at 10:29
  • This is something I stumbled upon while experimenting, and I thought this should be a simple software fix, especially if there is some simple note dropping issue. I did not imagine it taking a whole lot of man hours to fix. But I did not get any one appropriate from Casio to speak with thus far.

    My reason for posting was to check if other keyboards from Casio have similar issues.

    I could not believe myself when the Casio engineer asked me to go to a shop and check if this is the case by myself (they should be able to check this quite easily on their end).

     – SuMo Feb 06 '22 at 10:44
  • I have one Casio keyboard, and it has a bug which renders a certain type of sounds unusable, I've reported it and made a video, but I don't expect it to ever get fixed. There are many other fun things that can be done with the keyboard, so it's not a total loss. – piiperi Reinstate Monica Feb 06 '22 at 11:18
  • Why would you think it's a simple software fix? Does the piano have regularly scheduled firmware updates where the fix could be included or would they have to produce an one-off update? Does it even have an option for users to update the firmware? I have the feeling that setting these up would be several magnitudes more difficult than the actual fix. – ojs Feb 06 '22 at 11:21
  • No-one will ever fix this type of issue. If it gets out of the factory with a bug it will have the bug forever more. The team who designed it would be onto the next project before that one even hit retail. Usually these things aren’t firmware upgradable anyway (In theory they are, but not in practice) – Tetsujin Feb 06 '22 at 12:15
  • Maybe it’s some type of phase cancellation issue that happens over the length, layering and repetition of both samples. Have you tried using a longer series of notes, say a full octave scale or more? Like an earlier comment said, why layer two piano sounds? A guy goes to his doctor and says “Doc, it hurts when I do this…” He makes an unusual motion with his arm. The doctor says “Well then, don’t do that.” ;-) – John Belzaguy Feb 06 '22 at 18:09
  • I am not entirely sure the analogy of unusual motion is that appropriate. Casio allows tones to be layered, no caveats about layering piano tones. It works fine for all tones barring the piano tones. It does not appear completely out of the realm.

    I do not know if you have tried it, it just sounds richer to me. But then for passages which involve many keys with the sustain pedal pressed, it gives up soon.

    @ojs Firmware updates for different models can be seen on the Casio website. I am sure it is possible if there is a will to do it from their side. But we will see.

     – SuMo Feb 07 '22 at 12:07
  • @JohnBelzaguy Forgot to mention, yes I have tried with octave scale or more, and the issue still remains, it has nothing to do with the specific set of keys that I pressed. – SuMo Feb 07 '22 at 16:28

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