Accounts of Twain's lectures and readings that I've read mention his
frequent mumblings, and Twain mentions how much he admired Dickens for
dramatizing his characters in his readings.  In the recording by William
Gillette, he does at least one good "stage mumble" for effect and when
voicing the words of the characters he gives them different inflections and
accents. This hardly proves that Twain did likewise given the forty year
span between the impersonation Twain heard and the recording, but WG is the
closest we have with any kind of stamp of approval from Twain himself,
followed by HH who was blessed personally by Clara.

If you watch HH's 1960s TV performance it's a little disappointing compared
to what he does now. Like a good wine...

Kevin Mac Donnell
Austin TX