Meredith Willson on Charlie's "twiddeldy bits"

“The themes we use, excepting for a bit of Wagner and Brahms interpolation, are about half Mr. Chaplin’s and half mine, with my development and orchestration. And it’s uncanny how right he always is when technically he isn’t a musician and can’t read a note of music. In scoring the picture we’d run it through, then in this place or that one he’d sing a few notes; something he’d call a ‘twiddeldy bit,’ and it would unerringly work out to be exactly what the sequence needed.” --Photoplay, December 1940

Willson was Musical Director for The Great Dictator (1940) which received an Academy Award nomination for Best Original Score. But he is best remembered for composing the hit musical The Music Man. 

Willson & CC at the Chaplin Studios.