These kinds of tracks usually work well because the vocals are left evenly balanced between the two channels and that makes them easier to remove accurately.
Primus often has extremely unbalanced channels. This cancels out the vocals but leaves the rest in tact. Usually the vocals are put dead center, so we can split the stereo track and invert one channel.
Sometimes the bass is pushed more towards the right channel, rhythm guitar might be found more towards the left, and so on. Vocals are normally placed in the “center channel.” Stereo tracks have two channels, but not all of the instruments are balanced evenly.
