Hi, Ralph:
I'm sending your White Christmas back at you, with a few of examples of the things I mentioned.
I manually added some rather arbitrary pedal events into the piano (as well as dropping the velocity on the left hand at the first piano entrance -- just seemed a little obtrusive to my ears. Your mileage may vary.)
Don't be afraid of recording the Clavinova's pedal(s) to add expression. If it's already hooked up to playback, it's likely hooked up to record and it's just a matter of recording the pedal presses into a new track with the same midi channel as the piano. Likely the easiest way to ease into real time recording. Some high end synths respond to variable pedal depth, but most are just all on or all off.
I also treated the baritone solo as if it were an instrumental trombone solo and added some bends and vibrato. This was done manually. Basically, I just wanted to demonstrate how a little creative controller data can bring a part to life. Again, your mileage may vary: the swoops may be too much for your ear.
I removed the 8va bassa marks from the tenor and used Composer's Transpose Instrument Key (under the Staff menu) function to set the tenor line's transposition. Although it doesn't have an automatic setting for tenor voice, Composer does have many, if not most, transposing instruments in a selectable database.
And, finally, I played with the stereo spread (under the Staff/Setup menu) and set the sounds up as they may be on a stage. Just that kind of change can really fill the soundscape.
Lovely arrangement, by the way. They just don't write 'em like that, anymore.
David