Disklavier

I own a digital recording studio with some great digital pianos, but 
no actual grand.. and I have a good friend that has a Mark III model 
Disklavier.  I recorded some tunes at his house and brought the 
floppy disk home to see if I can import the .MID files into my MIDI 
sequencer, Performer 6 from Mark of the Unicorn.  On an old MAC, 
unfortunately.

Anyway, I looked at the PC-formatted floppy on my Windows PC and I 
see two files,

pdisk.mng
psong.mng

What do those do?

thanks

Karl