Background Vocals

[mindonstrike]

Just grabbing one of my Sound Choice Star series disks, It reads both on the disk and the back of the jewel case "Stereo performance tracks" (for 1-8) and "vocal demonstration tracks" (for 9-16). In addition each track 9-16 reads "vocals right channel only" under the title.
Most other manufacturers will use a similiar scheme such as "instrumental tracks" and "with vocals".
I didn't find it on the SC but many manufacturers will use the term "multiplexed" to indicate that there are tracks with vocals on one channel.

And by the way what you are trying to get rid of is the demo vocals that are their to help you learn a song, and as gduns said "background vocals" are on both channels