Joe, in the KHPro manual "Table Of Contents" you will find these hyperlinked entries:
Export Your Karaoke Song File
Replace Music with Vocal Reduced File
Create A Multiplex Song
If you click the second link above, it jumps you to this text:
Replace the Music with Vocal Reduced File
1.When your lyric highlighting is acceptable, click the Edit Lyrics button and the Add Music button to find and add an audio file without vocals. This file should be the same length as the first to preserve your highlighting.
2.Vogone reduces the vocals of most songs, and does not change the file length.
3.You can keep using the music file with the vocals if you wish.
Forgive me for not making it clearer.