Hi Adam, Welcome to Yamaha Synth!

Sorry you think you have an issue with your CP4 Stage. There is nothing we can diagnose via a video.

We can tell nothing really from your video. As there is no musical sound - we understand you are asking about the physical sound of pressing a key. But how hard a key is struck is always tempered with a musical result - you should not hit the keyboard with any more force than you would when playing.

Well, your gesture (striking a key with two fingers really, really hard), is somewhat beyond a musical gesture and is bound to make some physical noise. We cannot tell anything from your video about the sound you think is unusual. That kind of thing simply does not translate well via video - and sound on video. I've made a sofa pillow and screwdriver sound like a well tuned kick drum with mic placement and recording gear. So if there is something unusual about the physical sound, you'd do best to seek out someone with personal knowledge of the CP4 Stage. And let them play on it and evaluate the situation - video is not going to help in this case.

You could/should ask your dealer or you can call a Service Center if you think it is unusual or out of the ordinary (they may ask you to bring it in). But any keyboard struck as hard as you are striking that keyboard in the video is bound to make some kind physical acoustic noise - if you hit it with a hammer it would make a breaking noise... just as a hint - what you are trying to determine is if the noise is unusual, right? Not that it makes a noise?

Try hooking the CP4 Stage up to some music software and record yourself playing a musical piece as MIDI data - get used to what kind of effort it takes to hit a key and send the velocity to 127. Adjust the CP4 Stage's global Velocity Curve so that it is not too easy to get to 127. Remember 127 is as hard as you are ever going to hit a key to get volume. It is quadruple forte ffff. This will avoid you ever striking your piano with excessive force. There is NO benefit in striking a key with more effort than it takes to get a 127 result. That is not only the theoretical maximum, it is the absolute maximum value. This way any physical noise beyond the effort of 127 is meaningless because you never need to hit the key that hard.

Your local music store and/or your local service center, or anyone who also owns a CP4 Stage will be able to tell you if there is any excessive noise in your particular CP4 Stage. The hammers do not hit strings - there are no strings inside the CP4 Stage... so whatever they are hitting sound be measured against the CP4 Stage making musical sound - at the appropriate volume for the room you are playing in at the time. This is why your video is no way to judge what you are asking about. One has to be there with your CP4 Stage.

Hope that makes sense.

Hello,
Thank you for your reply!
OK, I can agree with you, it was brutal, I mean hitting these keys on the video, but I don't play this way normally. I will call a dealer and talk with him about that.