Mighty Bop said:

another thing where he is leading some kind of group trip thing (the one where someone in the background yells "Help! I'm drowning!! , and has all these other weird sound effects, etc).

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Deepman has this album in his "Psychedelic Culture Library" (as well as a lot of other Leary files).  You may get a message saying that too many users are logged on.  Just keep trying from time to time.  The album you're referring to is called "Turn On, Tune In, Drop Out (Soundtrack)".  Leary also put out another "Turn On, Tune In, Drop Out" album on the ESP record label.  It has no sounds, music or acting.  It was recorded one year earlier in 1966.  Click  here to download it courtesy of GratefulJim.  Also from GratefulJim, you could have  "The Harvard speech" circa 1962/3, as well as  "You Can Be Anyone This Time Around" from 1970, I believe.  "How To Operate Your Brain" is one of my very favorite Leary albums, but it's from the 90's. 

Mighty Bop said:

Did Leary and the gang record any video or audio while at the Milbrook location?

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I don't know if Leary and company recorded anything that has been released, but I've seen footage from Milbrook. You can see it on the LSD and Leary documentaries.

By the way, the Harvard speech is actually circa 1962 or 1963.