You can use the Realcharts instead of the audio for the piano. That way you would hear MIDI, which wouldn't have any ambient sound. But you get the same notes.
Typically extra sounds heard are mechanical sounds of the piano ( akin to hearing fret noise on a guitar). Or artifacts from transitions.
Sound of sustain pedal motion, squeaking chair, player breathing or mumbling etc etc These are noticeable if you listen to a solo track, with headphones on, and are listening for them, but usually not noticed in a mix. Of course many piano players make noticeable sounds while playing (Errol Garner for example. But in his case, his extra sounds just made things sound better, as with everyhing Errol did on piano!)

To use the Realcharts instead of the audio, choose edit copy tracks, and copy the MIDI to an unused track. then erase or disable the orignal track. you now have MIDI piano instead. use a nice piano MIDI sound like a Hi-Q sound

also, There are MIDI Supertracks available for piano, you could use those too.

Have Fun!
Peter Gannon
PG Music Inc.