A method and apparatus for limiting which player pianos can properly play
notes within a media file or stream without playing additional "bad
notes" encoded in the stream for disrupting the playback of that musical
composition so as to prevent playback on unauthorized systems. Bad notes
are encoded within a file or stream containing the proper "good notes" of
the composition along with control commands to allow identifying the bad
notes (e.g., by location, relative position, characteristics and so
forth). Player pianos of a first manufacturer, having the proper
programming, properly decode the control commands to locate the bad notes
and prevent them from being played back with the good notes, therein
properly rendering the musical composition. Player pianos from other
manufacturers will play all the notes thus obfuscating the playback of
the musical composition. Fidelity of playback on authorized system is not
affected.