Hi again.
I have a lot of experience with the SD35

(We are still using them. Yes, backseatelvis, I would be interested in purchasing another one in good condition. Also any Double Density 720k disks. Note that HD Disks formatted at 720 do NOT work)

It is NOT possible to connect ANY floppy drive, I am told it expects a specific model. Neither will HDD drives work as far as Roland knows.

Rob, If your own files do not work, it is probable that they exceed the number of tracks allowed in format 1. Limit for the SD35 is 16 MUSIC tracks, though other tracks with just control or text information do not count. If you want more, you have to create them as format 0. If your sequencer cannot handle format 0 (unlikely) there are conversion programs available.