DESCRIPTION:
"RaRCS" stands for "Record and Record Combined Stereo", which means that the left and the right parts of the video comes from two different studio records.
Regarding the current video, you can enjoy "Dominique" from the movie "The Singing Nun (1966)" by Debbie Reynolds: on the right side the official song published on disk (with lyrics), while on the left side the audio extracted directly from the film (tempo adjusted). As you can hear, there are little changes in the vocals (possibly remixed), and the music (performed by the string orchestra) were recorded newly. Links:
http://www.youtube.com/watch?v=DRbZLCjuqn8
http://www.youtube.com/watch?v=ckmFrXnfv80
http://www.youtube.com/watch?v=Qkq0Ncf32cs