[Malte Müller]

And operetta as the “lighter opera”, too.

Musicians just continued doing for film what they had done for the theatre.

Yeah, that’s not really unknown that basically all the first composers working in films came from that tradition and education. That was the “pop music” of the time at least the well known melodies. Only later other composers with different background like jazz and pop/rock changed that more. Maybe film music nowadays even is more “unique” or “specific “film” music than it ever was even if the cost is listenability (is that a word?)…