~~Oh ... I don't know anything about that ... ?~~

TMP ... ah nearly forgot. Literally walked away from writing this post thinking "wait a minute ... I have heard it outside of TNG ...".

Yea, interesting, hadn't considered that. Thanks.

Thank you! The compression and microphone points fit. And yea those glissandos definitely change the feel of the theme. IMO, they’re easy to miss but make a huge difference.

Thanks again!

Actually, if you've watched TNG's early seasons, you've already heard this unused theme, in bits and pieces.
The very first piece of music heard in TNG ever (that isn't the intro itself) is a slower, less energetic (more introspective I guess?) version of that unused theme.
The main leitmotif itself appears all over early TNG.
I figure that, when Maccarthy was writing the early filler music, he assumed that his theme would become the main theme, and so heavily leaned into it when writing the filler music. Obviously, the main theme was tossed - but not his other music.

Speaking of unused music, the final TMP/TNG theme itself was almost different:
https://www.youtube.com/watch?v=BbdhC-OXXa0

There's an interview where they tell stories, and apparently after they made this early version of the music, Robert Wise listened to it and gave the best three word critique ever - "There's no theme!"
Goldsmith basically went "...oh.", then went back and reworked what he had already into the 2nd version, and there you go that's the final theme.

Hilariously it kind of makes me think of like The Orville - you know all those "Star Trek" themes without copyright issues.

All the composers for Star Trek have been incredible in their own right. Everyone has their preferred (James Horner) but I have yet to not enjoy a Star Trek opening. And yes, that includes Enterprise. It tried to break the mold and failed, but I give it a pass because the visual sequence with it gets me still.

I will say that First Contact's theme is damn good. Especially when used at the end with the Vulcan meeting.

Faced with composing a new Star Trek theme for the film, Goldsmith initially struggled for inspiration, and proceeded to compose as much of the score as possible before the need to develop the main title theme. His initial score for the scene in which the newly-refit Starship Enterprise is revealed to the audience was not well received by the filmmakers, director Robert Wise feeling that it lacked a strong thematic hook and evoked sailing ships. Though somewhat irked by its rejection, Goldsmith consented to re-work his initial idea and finally arrived at the Star Trek theme which was ultimately used.

Jerry Goldsmith - Wikipedia

The theme is distinct. I had always correlated the theme with TNG until I watched The Motion Picture several years after TNG. I did not recognize that the theme was used in both. It's amazing because it almost didn't exist, and was composed after pretty much the rest of the score was complete. Goldsmith had to rework it because the director wanted a "strong thematic hook."

Ooohhh ... interesting ... any links or can you roughly point me to the part where shift happens? Inuitively this makes sense though that there's a kind of rhythmic drive that comes out midway.