The 35mm Grease stereo would have been Dolby Stereo (4-channel) which was introduced to theatres in 1977. A Star Is Born was the first film to use the 4-channel stereo, but it was Star Wars that really got it noticed. The theatre circuit that I was with at the time, put in five Dolby Systems just for Grease in their busier complexes, but only one auditorium, the big one, got the system. The smaller towns and second run theaters along with smaller auditoriums in the complexes that had Dolby Stereo when the print was moved down would have played it mono since the systems were not prevalent. The Dolby Stereo prints were backward compatible so they could play in a theatre with a Dolby Processor or on an old RCA tube sound processor at the Strand Theatre in Sulligent, AL.Originally Posted by GMpasqua /t/315277/lost-horizon-1973-the-complete-version/60#post_3860937
I saw "Grease" on opening day in 1978 at the Lowes State 1 in New York - it was a 70MM blow up and stereo surround etc ...a few weeks later I saw it again at the mutlipelx - it was 35mm stereo - but I don't believe it was 6 channel or anything like that. By the way, the 35mm version looked awful compared to the 70MM blow up. After a film played in stereo at a first run theater the second run theaters sometimes got mono prints.
Some theaters never even got the full version of many roadshow films which were cut by the time the opened in their cities.
It actually was not until the early 90's that major theatre circuits would equip all their screens in new complexes with some type of stereo system.