Indeed: https://en.wikipedia.org/wiki/FM_broadcasting https://en.wikipedia.org/wiki/FM_broadcasting "For this reason, the left (L) and right (R) channels are a

Indeed: https://en.wikipedia.org/wiki/FM_broadcasting https://en.wikipedia.org/wiki/FM_broadcasting "For this reason, the left (L) and right (R) channels are algebraically encoded into sum (L+R) and difference (L−R) signals. A mono receiver will use just the L+R signal so the listener will hear both channels through the single loudspeaker. A stereo receiver will add the difference signal to the sum signal to recover the left channel, and subtract the difference signal from the sum to recover the right channel." Other systems were considered by the FCC, but this one won (see article for the details) If you're interested in this sort of thing, the book Defining Vision is a great discussion of the history of HDTV.