Jonno said:
Here's what I've figured out so far about Planet of the Apes:
The original movie was mixed in 4-track stereo and mono, though there is some doubt as to whether the 4-track mix ever saw the light of day (there's a discussion on that subject here: <a href="<a href="http://www.filmscoremonthly.com/board/posts.cfm?threadID=71763&forumID=1&archive=0)"" title="www.filmscoremonthly.com/board/posts.cfm?threadID=71763&forumID=1&archive=0)"" target="_blank">http://www.filmscoremonthly.com/board/posts.cfm?threadID=71763&forumID=1&archive=0)"</a> title="www.filmscoremonthly.com/board/posts.cfm?threadID=71763&forumID=1&archive=0)" target="_blank"><a href="http://www.filmscoremonthly.com/board/posts.cfm?threadID=71763&forumID=1&archive=0)</a>" title="www.filmscoremonthly.com/board/posts.cfm?threadID=71763&forumID=1&archive=0)</a>" target="_blank">http://www.filmscoremonthly.com/board/posts.cfm?threadID=71763&forumID=1&archive=0)</a></a> - at least the majority of 1968 release prints were mono.
By the time home video rolled around, Chace did one of their pseudo-stereo mix jobs and this is used on all the laserdiscs that I'm aware of (which may not be exhaustive, but I've spent some time searching). DVD and Blu-ray brought questionable 5.1 mixes to the table, BUT the Blu-rays do feature the original mono mix as well so this is the best source that I'm aware of.
It's a similar story for the sequels, though in their cases there was no question of an original stereo mix since they were only ever released in mono. They too follow the path of dubious home video remixes followed by a solid preservation of the original mono on the Blu-ray.
I'm prepared to be corrected on any/all of this, particularly if anyone has more info on the original theatrical releases or laserdiscs that preserve the mono tracks as PCM - this would be especially welcome in comparison to the BDs' basic Dolby Digital.
I think you've nailed the timeline down pretty good. In the late 60s Fox was working very hard on keeping costs down - still rebounding from the studio nearly going broke making CLEOPATRA just a few years earlier. And with multiplexes on the rise and this not being a musical, it is not a surprise there are no confirmed original stereo showdates.
Of minor interest, there are existing stereo music tracks that have used for the soundtrack CD issue, and were also used for the 35th Anniversay DVD 5.1 remix, which is the remix I prefer over the Bluray 5.1 remix. I don't know why, but the 1st APES movie has had a few remixes on home video over the years, - even the different DVD releases have had audio differences. Going back to the bluray, while it is not my favorite remix, it does have the original mono track and an isolated 5.1 music track. Once again - Kudos to Fox for offering original mono as a audio option.