Anyone know of software like this?

[Ernie]

I don't know if there is any software like this or not. I am looking for some software, where you could mix karaoke songs. I don't mean adding a bunch of full karaoke songs together. I would like to sing part of a karaoke song, then have it transition (flow) into another karaoke song, where you wouldn't notice a huge change in tempo or the music as it transitions. You would be able to incorporate several songs, one after another. I hope I haven't confused anyone.

Thanks