The title refers to the main character who lives in a bleak future. The film plays in some sort of factory / living commune in which everybody is obliged to follow orders. ‘The system’ has its way to keep the workforce quiet, such as forced medication, rigid control and consumerism as religion (“Let us be thankful we have commerce. Buy more. Buy more now. Buy. And be happy.”)
The film is somewhat vague and not always easy to follow. Also there is an overwhelming amount of ‘surrounding sound’. Talking speakers, whistling noices, broadcasters, etc. That does make the film noted for another watch some day, since it is interesting enough for a second round.
The stages vary from minimalist (all white) to elaborate machine cities including some amusing findings for its age.
“THX 1138” is not a masterpiece. The 6.8 at IMDb is a bit on the low side in my opinion, but would not need to be much higher. Like I said, it is a descent and enjoyable film. A scifi classic. It seems that four years earlier Lucas made another film with the same main character. Let me see if I can find that one too.