I had once a PSR6700 sold it 2 years ago for $1200. Excellent work station. It plays DOC
format file only. I still have plenty of these
discs. You cannot play standard midi files using
the psr6700 disc drive. You need a midi filer
disc drive which I still have too and is in excellent condition. You need to connect it vis the serial cable to the midi in in the back of thekeyboard.
email me I can get you through it.
my name is tony azar (858) 621-5473 tazar@logicon.com

Tony