Quoted from Sunfox:
I know you aren't actually interested in this... but The Wizard of Oz is interesting in its sound production. Of course, everything was mono 1939, but instead of using the then-common movie practice of recording music by placing a single microphone in front of the orchestra, with WOZ they used multiple microphones placed all around the stage, each recording groups of instruments onto separate tapes. These were then mixed together into the mono master.
Those original recordings survived, and were used in the 90's to compose a proper stereo/5.1 soundtrack. Thus, although it was originally released mono, WOZ is one of the oldest movies with actual stereo sound.
Having acted in many movies and played in my fair share of bands, recording technique is always of interest to me.
Thanks for the info!