Trailers today do it all the time! For the reason stated... the actual score isn't finished yet.
I thought you were talking about the actual MOVIES. And, as I said, that doesn't happen much, if at all, anymore.
It did, back in the '30s and '40s. Not regularly, but it happened. Those were "movie factories" in the Golden Age, and they recycled costumes, sets, music scores and everything else to turn out (as many as) 50 movies at a single studio.
Since The Wizard of Oz is my favorite film of all time, I'm particularly aware of its recycled elements:
Jeanette MacDonald sings an operatic aria in the movie "San Francisco" wearing the dress that would become Glinda's gown by adding puffy sleeves and a few more sparkles.
The tornado footage was used again in Cabin In the Sky.
The music from the witch's castle played while the foursome tries to escape is the same music played in "Marie Antoinette" while the royal family tries to flee Versailles.
Some of the score from the Kansas scenes, particularly the music leading up to "Over the Rainbow" was used many times, including under a short Christmas film featuring Joan Crawford and her children.
Toto (the dog) shows up in the first shot of "The Women."
Dorothy's basket that she carried with her in Oz was used in many movies, but you can see it in "Little Women" with June Alyson.
The bridge crossing over into the ravine where Professer Marvel's wagon is set up was used in "Gone With the Wind" when Scarlett is fleeing Atlanta with Prissy, Melanie and her baby.
It was a different era.
"Jaws is the Citizen Kane of movies."
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