IEEE MILESTONE IN ELECTRICAL ENGINEERING
             AND COMPUTING

        Invention of Stereo Sound Reproduction, 1931

Alan Dower Blumlein filed a patent for a two-channel audio system
called “stereo” on 14 December 1931. It included a “shuffling”
circuit to preserve directional sound, an orthogonal “Blumlein
Pair” of velocity microphones, the recording of two orthogonal
channels in a single groove, stereo disc-cutting head, and hybrid
transformer to mix directional signals. Blumlein brought his
equipment to Abbey Road Studios in 1934 and recorded the London
Philharmonic Orchestra.

                          April 2015
                                                 IEEE