The things I have tryed:
- reïnstall yamaha cp4 midi driver
- searching a hell of a lot of options in REAPER to prevent this problem.
- setting some MIDI things like "local" in my piano to "off"

Hi, Welcome to Yamaha Synth.

Your problem is a real one. We'll start by eliminating the things you've tried. It is unlikely that it is a driver issue. Mainly because a driver works or doesn't work, it is highly unlikely to "break" like this. I don't like the word impossible, but if it could be used, this would be an instance. Searching the options in your DAW, is a better streetlamp to look under since, DAWs can (on purpose) apply an offset to your velocity data, and so can the receiving software instrument. It would be some kind of Velocity Offset.

When working with a DAW, you should always turn Local Control to Off, the fact that you think this might change something (other than preventing the keys from triggering the CP4 Stage sound engine) says you are really grasping at straws. Local Control just prevents the "local" instrument from responding with its own tone engine, allowing you to select the receiving tone engine by routing the current MIDI Track's MIDI OUT.

Just so you know: this issue is the major drawback in using any software synth, the fact that you are at the mercy of your configuration, in other words, having seen how meticulously the manufacturer of a hardware instrument is accomplished... having seen the lengths gone to to work on instrument action and tone generator response time. That is part of what you pay for... the fact that someone with test gear is looking at this very thing, the fact that it is evaluated, studied, and tested... not only by machine but by living/breathing musicians is worth the effort in results. And while you insist it is not latency (and it may not be) perhaps it is CPU... your virtual instruments vital specs change depending on how much else your computer is tasked with doing at any moment. Having 36 bands of EQ open might bog down the works... it can vary.

There is no one matching your external controller to the response of your virtual instrument. You kind of are at the mercy of the setup and your available resources. Now, that said, your problem sounds extreme, so you are correct in looking for a solution or a setting. It is highly unlikely that default setting would cause such a issue, but since this is potentially something you can control, you will need to search (not so much the DAW) but the virtual instrument you are triggering. If it has parameters that effect its response to velocity - search there.

I recommend you record the CP4 Stage, and compare the results to recordings of the virtual instrument.
Then have a friend (hopefully another musician) listen to both the CP4 Stage playing back the data, and then the virtual synth playing back the data... make it as true a "blindfold test" as you can. This way they answer with their own perception. Listen for their comments... see if you agree or disagree. See if they hear what you hear or if it is not something that is at all detectable.

The reason I recommend that is because, we, as musicians can be so close to our own performances that we cannot separate what something sounds like from what it feels like. Your friend will not have that issue, and can, on one level, be more objective.

Also see if you can hear the difference in the performance. With LOCAL CONTROL Off, you should be able to easily switch between the virtual instrument and the CP4 Stage as the target for the MIDI Track's OUT.

Also if the CP4 Stage plays back with the same obvious difference/anomaly in response, then you can focus your Search on the DAW some how changing your velocity data...

Let us know.

Bad Mister,

to start I want to thank you so much for your very quick response !

I've been doing a lot of recordings with my yamaha cp4 before I knew how good virtual instruments are. And I can tell you by looking to my old video's when I was recording my cp4's piano's that there was no problem at all.
Also if I open any virtual instrument let us say kontakt 5 in standalone mode, and I just play for fun there is also no problem at all! There is also no problem if I just open my virtual instrument in my DAW (REAPER) and just play for fun. < thats the big thing I don't understand!
I can play as sensitive and nicely as I want like playing on a real grand, it is just ONLY that record button to record my MIDI notes that does this..

Yesterday another musical friend of mine came by and I asked him if he heard the difference between playing while recording and playing while I am not recording, he has excellent ears and he told me blindly that there is a difference.
The recorded version sounded more stacciato with less emotion and the version while I was not recording sounded like a charm! (I played the same pieces with the same velocity and the same speed).
I am also not a fan of the word impossible like you've mentioned in your reply, but I think it is almost impossible that the issue lies with my Yamaha piano, if it was my piano which caused this issue, then I would also have this problem while I am not recording am I right?

It might be the DAW which causes the issue and I haven't found an option to adjust the velocity while recording MIDI yet. I've tryed a trial version of REASON 9 DAW to check if it had the same issue but I was more struggeling with the interface than taking care of my problem, (REAPER is like the only DAW in which I can work) I'm so used to it..

I hope changing DAW's is not the only sollution to this problem, we'll see

I would like to thank you already to help me with this troubleshoot and I hope you can offer me some more tips! Because the only thing I can is playing the piano and virtual instruments and a little mixing. I am a real noob in the core of MIDI and AUDIO and I am trying to learn more about it every day.

Musical greetings from Belgium

First, I've recorded MIDI using Reaper and did not experience this issue. That was some time ago, though, so things may have changed.

I agree with BadMister that it's more likely to be a Reaper setup issue. The first thing to check is whether the track volume control is adjusting MIDI velocities, so that MIDI output velocities are lower than the input velocities. Try adjusting the track volume to full up and see if that changes anything.

If you're using Windows, another way to check is to install (free) MIDIOX to view all MIDI messages as they come into and go out of the computer. That way you can press a key, see the velocity coming in, and see the velocity going out. If they're not the same, then it's definitely Reaper, and you can take this issue to the Cockos forum.

Setting up MIDIOX can be confusing, but you can probably get help on that at Cockos forum. If I remember correctly, if you're just using it to monitor as in this case, it should "just work" without any particular setup.

Good luck, and keep s stiff upper lip, because MIDI and digital recording can get very complex and confusing. Once you get a good method sorted out, though, it's a dream and beats the crap out of the bad old days of tape and everything audio!

I got pretty advanced in my use. One of the tricks I used was to sample my digital piano and make a soundfont, so I could continue working on songs with piano parts using MIDI and the soundfont when my piano was still in the case. The soundfont is of course a good few steps down from the quality of using the CP4, so of course I'd always re-render the track before final mixdowns. But it was useful for doing things like fixing piano flubs or adding/subtracting a note or phrase here or there.