OK, I misunderstood. If Chaplin just came up with a few notes and not a whole melody with pitches and rhythms, that's different.
I'm all for Chaplin being credited for his "songs". After all, he wrote "Smile" which was from "Limelight." That is HIS...just as Carly Simon's song from "Working Girl" was hers.
And Irving Berlin and Bob Merrill, et al, were given just and due credit for their songs as they should have been.
But your comment above IS my argument...counterpoint, changes in keys, placement (Chaplin did tell his arrangers WHERE to put the music, to be fair), etc., is the "scoring" effort I think of in film (not the songs on which musicals succeed or fail).
I realize, of course, that the argument can be made that these folks are "arrangers" and/or "orchestrators" and not composers.
But I think sometimes a very fine line is drawn between arranging/orchestrating and composing. Chaplin never had a clue about most of that. He had a melody in mind and he knew where he wanted it to appear.
In fact, the most famous collaborator he had among Hollywood musicans was Alfred Newman, who did the honors for him in the movie "Modern Times." Newman, the score's conductor, and David Raksin and Edward B. Powell all worked from Chaplin's "whistles", to provide material to fill in where Chaplin's whistling couldn't. Whatever "original" material any of those men contributed never was credited. The credit read "Original Music by Charles Chaplin". And it may be Chaplin had whistled more than one theme...certainly, the melodic memory anyone has of the films he made are due to Chaplin.
Chaplin always got sole credit for the score. But IMO, it was always a song he "composed". The rest of the score was "adaptation" rather than original composition.
Of course, that's movie scoring and not the same thing as musicals for theater or screen.