UPDATE: Ralph the Sacred River explains Dylan's moustache. And let me add this: Dylan has never used the word "moustache" in a song, though he has twice used the word "beard" (including the "very weird" statement "I like Fidel Castro and his beard," chosen to provoke the farmer in "Motorpsycho Nightmare" into throwing him out of the house.)
ANOTHER UPDATE: If you spell "moustache" "mustache," however, you do get a very famous one:
Inside the museums, Infinity goes up on trial
Voices echo this is what salvation must be like after a while
But Mona Lisa musta had the highway blues
You can tell by the way she smiles
See the primitive wallflower freeze
When the jelly-faced women all sneeze
Hear the one with the mustache say, "Jeeze
I can't find my knees"
Oh, jewels and binoculars hang from the head of the mule
But these visions of Johanna, they make it all seem so cruel
An emailer had to remind me. I should have remembered this one! I have actually blogged at length about these lines before. To that post I'd add that the presence of Mona Lisa and mustache in the same verse ought to remind us of the famous Marcel Duchamp artwork, especially since "mustache" halfway reappears right next to Mona Lisa in the form of the word "musta."
So which is the right spelling? According to the Columbia Guide to Standard American English, "mustache" is more common, but "moustache" is not entirely a British spelling. Anyway, looking up the spelling question, I ran across this, which is kind of funny.
There, now, have I made up for my earlier, woeful omission?
YET ANOTHER UPDATE: My comments on the actual show are here.