The music is 1970s, but the actual movie is 1921, I guess? Either that, or he means that the music was written in the 1870s. I don't know when Charlie was born or died though, so I can't really say.
EDIT: I'm pretty sure it's the former though. I just did the math and I realized Charlie would have to have been in his seventies by the time of the movie, if not older than that in the latter scenario!