Garry,
Have you tried searching for midi files of the songs you want? I sometimes want songs that have no background singing on them and will go to midi-hits.com and see if they have a version of that song. No midi files have any vocals at all. Also, midi-hits.com will also do custom songs also. If you have a song or two that you really want and will never come out on karaoke then this is an option. I think about $80/song though. Yeah, you would have to want it pretty bad, but maybe someday I will. If you have some midi software like Cakewalk or something like that you can even alter the synthesized sounds to more suit your taste.
You can also just buy the song in mp3 format if you totally like the way it sounds already or midi files would not benefit you at all. They have sample snippets of the files they have. I think for one song they already have is $8.95. There are of course other midi files sites too. Don't really know about any others though.
As for creating medleys, I think your best bet would be sequencing software. I'll also say that I think there is software out there to help dj's create dance mixes that might also work to help piece together a medley.
Just a thought.
Later,
Wally
