MIDI Mode = Single Channel for Montage should be best when working with the Clavinova as the Clavinova does not, that I can tell, transmit simultaneously on more than 3 parts (main, left, and layer).

The reference manual shows a "Master Keyboard" mode of Clavinova. This is like the templates in Montage. (Outside of clock) The manual doesn't delineate completely what this mode does - but it indicates this is best when controlling external hardware.

When using any external controller to master a synthesizer - there is usually some tradeoff because not all buttons/sliders/etc are "at your fingertips" of the external controller. This can be remedied somewhat by having the slave keyboard (in this case Montage) in close proximity to allow local fader/button/ribbon/etc pressing.

Gustavo,
When you say the following "For someone not very experienced in the MIDI world, what are the settings I need to put in both keyboards to make my clavinova sound like the MONTAGE?"

To be clear, the Clavinova will never 'sound like Montage'. What you can do by connecting the two via MIDI is control the Montage when you play the Keyboard of the Clavinova. The sound of the Montage will still be made by the Montage, and the sound of the Clavinova will still be made by the Clavinova.

It is not clear what you are expecting (from what you've written):

1) you say you enjoy the Styles and feature is the Clavinova, does this mean you want substitute the Montage sounds for the Clavinova's own sounds? That is, have the Styles of the CVP cause the Montage to sound.
2) or do you simply want to use the 88-weighted keyboard of the Clavinova to play the Montage.

If the former, since the Clavinova transmits on 16 MIDI channels simultaneously when playing a "Style" or a "Song", you would need to select an appropriate Montage Part to replace each of the sixteen sounds that the Clavinova uses for each Style/Song. On a scale of 1-10 in degree of difficulty, this would rank above a 9... (just FYI) as many of the sounds in the CVP may have been especially made for the Style.

If the latter, simply connect the MIDI Out of the Clavinova to the MIDI In of the Montage, match the MIDI channel. The CVP can transmit on three MIDI channels from its keyboard.

Let us know what type of thing you want to accomplish...

Just some background, each of these top of the range products have their own particular strengths. Each is designed to be a complete experience on its own. Access to the realtime controllers on the Montage is as critical a thing as having realtime access to Intro, Section, Fill-in, and Ending buttons on the CVP709. So the physical setup may be a problem.

If all you want is the 88-weighted action keys, I would highly recommend getting a MONTAGE 8. Being a synthesizer, hands-on Control is going to be essential at some point.
If you are thinking of substituting Montage sounds for all of the Style controlled sounds... you'll find many of the Clavinova sounds may have been specifically created for use with particular Styles... and there may be no Montage equivalent.

Other things you can do with all this cutting edge technology
Other areas of interest could include, routing the audio output of the 709 into the A/D Input of the Montage, using it as a modulation/Clock source for the Montage synth engine. In this case you can use the sounds of both, or simply hear the 709 as it modifies the Montage synth sounds.

Many thanks for your replies. Indeed, what I had in mind is to use the great keys in the clavinova cvp to execute Montage's performances. However, you are right, having easy access to control of all the bottons in the Montage is essential to really exploit this syntesizer. True, one can use the clavinova cvp to play a particular sound of the Montage (and even use the super speakers built in the clavinova cvp). However, the clavinova has great voices by itself to enjoy... If one likes playing, performing, composing and recording like me, the clavinova cvp and the Montage are two excellent keyboards but they complement each other (and mainly through a computer for the mixing process, since the Montage does not have a sequencer to record songs in the typical way). And MIDI-wise, it is easy to use the CVP as the masterkeyboard, just follow the templates given by the CVP...

Congratulations on the bolg, very useful!