Melodram and opera comique

I've been listening to a series of operettas (?opera comique) of Messager
bcast on Hector, live performances from 50 years ago or so. I will spare you
my reviews of the performances and the individual operettas (although the
one from last week, Passionement, which features an American couple in Paris
speaking French with mid-West American accents, is wickedly funny - I
wonder if Messager did one of a German couple visiting Paris?)....Well, be
that as it may, listening to three or four operettas in such a brief time
period is unusual for me, and it seemed to me that there might be some
relationship between opera comique and melodram. It's not a matter, I think,
or these operettas having such a high ratio of speech to song, or the fact
the melodies are relatively more straightforward than their "true" opera
cousins, but "something" seems related. This may all be a wild fois de gras
chase, but I thought I'd ask anyway.

Thanks in advance.