The film was released in Mono at the time, and in Mono on DVD.... I have since found the 4-track stereophonic recording, and have now matched it to the film, frame-by-frame, as a geeky project of mine....
So, for the first time ever, you can now see and hear Glenn Miller & His Orchestra in High Fidelity Stereophonic Sound. As recorded. As far as I know, this is the only stereophonic representation on the internet of this sequence.
The film is called "Sun Valley Serenade", Starred Sonia Heaney and James Stewart, and features the Glenn Miller Orchestra. It was made in 1941, and 20th Century Fox were experimenting with Stereo and 4-track recording, more than a decade before "Stereophonic Sound" made it into cinemas (which happened in about 1952).
All Rights acknowledged to 20th Century Fox, and this is here as a historical record of technological innovation in film-making, and also charts the fact that at 04:57 you can see the join where film distributors in the 1940's could make a cut in the projection reels to remove the beautiful Dorothy Dandridge, and the Nicholas Brothers - this being a common practice especially in the south of the USA at the time. Shameful.