Dear John,

I am quite familiar with this issue, and this is what you should do:

All pre-PSR-630/730 models use a proprietary file system for the Disk Orchestra. Luckily the PSR-630/730 inherited this. Meaning; although it now uses the FAT file system, it is still capable of reading the old proprietary disk format. Even the PSR-620 had FAT support, but used Yamaha’s proprietary file system when formatting.

You should lay your hands on a PSR-630/730 and use it to copy the content of the proprietary disks to a regular FAT disk using the build-in copy function. It has worked for me! (PSR-730)

Good luck,

Steven