It turns out the thread involving interviews with the great comedians of silent movies will be another brief one; while Chaplin and Keaton wrote memoirs, Harry Langdon, Charley Chase and Edgar Kennedy all passed away in the 1940's, so no interviews of them appear to exist (certainly no extensive ones), outside of some Hollywood trade paper and newspaper articles. The urban legend goes that Jerry Lewis spent quite a bit of time with both Chaplin and Stan Laurel, but one suspects that whatever was said between them will remain confidential.
The great Harold Lloyd, whose films are still unequaled in their blend of comedy and thrills with the action hero ethos, periodically made public appearances at screenings of his great 1920's features, and also released feature-length compilations of excerpts from his classic movies.
Here's Harold in 1962, interviewed by Harry Reasoner on CBS-TV interview. Enjoy.