I'm new to this forum so I'll start with a big hello to you all.
I am a music and sound lover and a self-taught pianist. I bought a Clavinova CLP970 back in 2002 and am still quite happy with it.
The only serious issue with the CLP970 GrandPiano1 main voice (which seems to be shared with many other Yamaha DP's, according to discussions in this forum) is the short sample loops, which result in an a quite sterile, dead-sounding decay.
After some experiments, I found out that the decay sound can be somewhat improved by layering it with a copy of the piano sound with a small detune. Yes, this is old school stuff, but if you attenuate the second layer until it is barely audible, you will just get that extra bit of beating to make the decay less dead.
Here is the best settings that I found so far (for MAIN and LAYER, respectively):
1/ Voice: GrandPiano1 / GrandPiano1
2/ Octave: 0 / 0
3/ Volume: 112 / 48
4/ Pan: C / L8
5/ Detune: +1
If you want even more beating, you can increase the layer volume up from 48, but you'll quickly run into the cheap honky-tonk effect.
Hope this can help somebody.