open sesame vs dictation

open sesame and dictation both are nouns.

Word	Noun	Adjective	Verb	Adverb
open sesame	Yes	No	No	No
dictation	Yes	No	No	No

As nouns, dictation is a hypernym of open sesame; that is, dictation is a word with a broader meaning than open sesame:

Other hypernyms of open sesame include bid, bidding, command.

open sesame (noun)	dictation (noun)
any very successful means of achieving a result	speech intended for reproduction in writing
a magical command; used by Ali Baba	an authoritative direction or instruction to do something
	matter that has been dictated and transcribed; a dictated passage