Wouldn't the first such patent (2+-signal stereo) be that of Clement Ader
US Pat 257,453 Telephonic Transmission of Sound from Theaters
His Earlier Fr Pat = Aug 9, 1881.
In a message dated 2/12/2017 1:51:17 P.M. Eastern Standard Time,
[log in to unmask] writes:
> The earliest patented solution of stereo sound on film was by W.
> Bartlett Jones of Chicago, whose USP 1,944,182 was filed 18 November
> 1930 and patented 23 Jan 1934
> He was the pioneer in stereophony, years ahead of Blumlein, Maxfield,
Harrison, and Keller.
> Jones' first work in stereophony was put officially to paper in 1927 and
published in several other patents. It is difficult to see that Western
Electric could have avoided taking licenses if they wanted to commercialise
Maxfield's or Keller's contributions. We have not heard about that.
> Keller and Rafuse USP2, 114,471 filed their application on the
individual recording of each groove flank on 20 June 1936.