"Tommy" was an odd case in that it was "Quintophonic". Basically, it was QS with an additional discrete center channel.
Check some movie and theater history. Dolby surround.
Not QS. As far as I can recall, dolby surround was the first
format to use a matrix technique in film, and they only did this to overcome the limitations of 2 track optical.
How in the world would someone do 4 matrixed channels
and one discrete and why?
How would a theater play this back?
You could do a pretty fair forgery of it though, since you could pan across three front channels and mix in just enough surround to fool people who weren't listening _too_ closely.
By the way, both "Tommy" and "The Song Remains the Same" were also released with magnetic prints, as were several other early Dolby titles. In fact, I've been told (but have no way of verifying) that the last 35mm magnetic issue in the U.S. was "Yentl".
I would certainly suspect that these films were released in other formats for distribution. Not all theaters would have upgraded to the new dolby format (thank god!)
Those magnetic tracks were delicate, but they sure sounded good!