[Keith.]

New Scientist 24 Jan.,this year in their feedback column has a paragraph on
this ,and this is a reference in Wikipedia.

a..
a.. ^ Duke Ellington and His Orchestra made some accidental stereo
recordings (a medley consisting of East St. Louis Toodle-o, Lot O' Fingers,
Black And Tan Fantasy), on February 3, 1932 for RCA Victor. It was a fairly
standard practice in that era to record using more than one microphone and
disc cutter. The various versions could be compared, to see which had the
best microphone positioning. It also allowed for safety masters in case
something happened to the original. Although the records are fairly rare, a
collector had both versions and noticed that while they appeared to be the
same performance, the sound mix was different on each. When the two
recordings were synchronized, it became stereo. The resulting recording is
available on the 22 cd set The Duke Ellington Centennial Edition.

Any further knowledge of this out there?

Keith.