The technical information is in the CP4/CP40 Data List manual. See p. 21.

If you didn't get one with the CP4, you can download here:
https://usa.yamaha.com/products/music_production/synthesizers/cp_series/downloads.html

That is helpful. Thank you. However I still did not see these parameters explained. I did however discover a lot of what I was needing to know thanks to you. I found a great way to hear this effect and all the various parameter changes and what they do. I thought I’d share how I did this.

The first thing I did was go to the wet/dry parameter and turn it all the way wet. That way I can hear just the effect. Then I went back and fooled with these parameters:

HiReso seems to change the frequency that is accented in the resonance effect while you are pressing the pedal. This might be a cool way to make the resonance as crisp or as dull as you would want.

PdlReso seems to change the speed in which the effect begins after you press the damper pedal and also the speed in which the effect goes away after you release it. I guess you would adjust this to taste, whatever seems to sound most natural to you. Or as different as you need for anything.

DmpCtrl seems to mean, how much bleed do you want? For instance, do you want a little resonance to always be present even if you are not pressing the pedal? If so, turn this up above zero. If you want a nice clean on/off, leave it at zero. The pedal can do absolutely nothing if you turn it to 127.

HPF is a high pass filter. Which means it lets the higher frequencies ring out and it cuts the lower ones wherever you set it. I would think you’d want to bring this up so you don’t’ get a lot of low-end rumble. All the good stuff for piano resonance is in the high end in my opinion.

LPF is a low pass filter. Which means it lets the lower frequencies ring out and cuts the higher ones wherever you set it. This goes up higher than a human can actually hear. But I think you can play with it and find out a nice place to set it. If it gets too crispy, bring down the frequency.

Low Freq and Low Gain seem to be an even finer adjustment than the HPF. Set the frequency you want to boost or gain, then move over to “gain” and boost or cut it to taste.

Then I went back and turned the wet/dry back to something more reasonable.

I could be wrong on something here and I hope someone does chime in if I am. But I hope someone else finds this helpful. This is a powerful effect and to know exactly what it does might even be useful in some other ways.

I did not see anything like this in the manual or on the downloads section. Maybe I just missed it! But nonetheless, here it is.

This is what the data list manual had to say. Helpful, but not complete.

Thanks. Also check out the more descriptive info in the Yamaha Synthesizer Parameter Manual.

For example:

- definition of Cutoff Frequency (p. 13)
- definition of Resonance (p. 14)
- LPF diagram (p. 16)
- HPF diagram (p. 17)
- Damper Control description (p. 57)
- Hi Resonance description (p. 60)
- Pedal Response (p. 64)
etc.

If you combine all this with the specific parameters shown in the Data List manual (I thought that was all you were looking for initially), you can flesh out your descriptions above even more.

Wow. Thank you! This is exactly what I was looking for. If it came with my keyboard, I must have misplaced it. Thank you so much. Perfect. I'll dig in. The Yamaha Synthesizer Parameter Manual link is below if anyone else was wondering. Home-run m.