Buying some midi cables will help you a lot. I have never found any software that will read the SY77 file format Txx. That source code that I mentioned is the only thing I've seen and I can't figure out how to use it. There is also a program on that same site that converts Txx files to syx voice data files but this will be of limited use to you I would think.

Once you get the midi cable you can record your sequences/songs into a software program like Cakewalk and save as a midi file. I've had the SY77 for many many years so if I can help with anything just post a question.