Ahhh...

Why DID NOT Dylan have in his kit a correctly keyed harmonica?

Musicians (folk in particular) are freqently like Magicians.

So much lies in the lie of "spontaneous illusion;" it is part of the performance.

Sincerely,
Gargoyle

Unlike Keith Moon (who might not be relied upon to finish a live set) Dylan anticipated/excepted to have the strength to perform "curtain calls" that is why the acoustic was always available in the wings.