If you have Winamp on your computer you can get a great little plugin for it called Streamripper. It will copy the radio streams (as mp3 files) from Shoutcast.com where you can find loads of radio stations. You can even set it to record a specified size of file, so you can set it and leave it. Then convert to WAV and burn it to CD. It can then be copied to your Minidisc machine. There maybe easier ways of doing it but this will retain the original sound quality without adding the sounds from your computer.