Maybe I can help you. Some years ago I had a MC 500. Now I found an old Disk with written "MRC-500 copy" on it. You can have it if you want for free. I cannot garantee it works cause I didn't use it for years. Just let me know if you want it. Greetings WW
I'm not familiar with the MC-500. Was the system disk on a floppy? Roland UK supply a lot of system disks for older gear. Normally if they still have the software you can send them a blank floppy and they will make a copy for you free. It maybe worth a try! good luck.... If not try contacting Delatronics in the UK they may be able to help. http://www.delatronics.co.uk/news.htm
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Waveviolator - Vintage Roland Effects http://www.btinternet.com/~waveviolator