Funny thing about Dylan, I was watching some film of him at the Newport Folk Festival a year or 2 before he went electric, singing Chimes of Freedom, every word clear as a bell, FAR clearer than yer Roger(Jim)McGuinn a couple of years later on the Byrds' first album. Mumble? Not that song. Maybe some other songs that I missed. But so much of today's singing comes out through a blanket. Dear ol' Bob, OTOH, has the clearest mumble I ever heard.