Disklavier

I just posted a link for some software that you may find fun to tinker 
with.
http://dp70.dyndns.org/mid2pianocd/

MID2PianoCD is a software utility for Windows which allows you to 
encode MIDI and ESEQ music files into the special CD formats required 
for various types of electronic player piano systems. These are CDs in 
which one audio channel contains audio accompaniment while the other 
audio channel contains a digital control track for the piano (sometimes 
referred to as "analog MIDI").

If you want to make a CD in which the piano accompanies an audio track 
(like some of the commercial CDs for these systems), you will need a 
software package for editing WAV files (a Google search for "wave 
editor" will list many choices). A decent FREE audio editing package 
that will work for this purpose is Audacity. Another good audio editor 
is Adobe Audition (formerly known as CoolEdit).