I have a lot of karaoke music. Can I use some of them long with Magic Music Maker to add sounds and instruments to make the music already there sound the way I want it to sound?

Yes, but be careful of redistributing music made by someone else... it depends on your intentions of the finished product.
Justin

That is a very generic question.

Yes, you can take any MP3 or Wave file and drag into the music maker. You can analyze the Beats per minute (Remix Agent) and add sounds to it.

If this will change the sound the way you imagine...I cannot tell you

Cheers
L