The situation as explained to me is that in the late 1990’s, my brother’s employer purchased a Yamaha Mark II XG “Baby Grand” piano ... or so back, the piano’s Disklavier DKC500RW ...

This means that any modern piano with an appropriately equipped YAMAHA Disklavier system can read a MIDI file and parse the commands inside to play the notes. Pianos with a Disklavier system ...