Sum and Difference Multiplexing and Why it Isn't Used with Vinyl Recording

Stereo audio hides some fascinating math under the hood. This video walks through how sum and difference signals are formed and how they let us recover the original left and right channels. Then we take that understanding into the physical world, examining the geometry of the stereo record groove and why the 45/45 cutting system creates the illusion of L+R/L–R encoding even though vinyl doesn’t use it. Finally, we zoom out to see how true sum/difference multiplexing powers FM stereo broadcasting and influenced discrete four‑channel vinyl formats This video is a followup on my video about vinyl recording:    • Vinyl Recording - Solid-state Devices and ...   It is also partly in response to the video about vinyl recording:on the Technology Connections channel:    • How do vinyl records hold stereo sound?   Thanks to @major__kong for correcting my atrocious math. The formulas should be: (L+R)+(L- R) = (L+L)+(R - R) = 2L (L+R)-(L- R) = (L- L)+(R-(-R)) = 2R Here's the video I link to in the hacked-in annotation. It shows a spectrum analysis of the stereo FM signal:    • How does FM stereo #broadcasting work? #Br...   Here is the Concerto for Contrabassoon and Orchestra by Victor Bruns:    • Concerto for Contrabassoon and Orchestra (...   Vocademy - Free Vocational Education vocademy.net