Excuse me, but serial interfaces for Korg/Yamaha etc.?

How 20th century... No-one's used serial for quite a while now (maybe with the exception of Ketron).

I don't think this is the info Shim is looking for, Mac.

He just wants a reasonable MIDI sequencer/editor that will run on an older PC. Maybe a used copy of Cubase VST5 if cheap enough would be what I would recommend... I've used it since the Atari days, and it, IMO, is the best thing for MIDI, ever!