pipework vs organ stop

pipework and organ stop both are nouns.

Word	Noun	Adjective	Verb	Adverb
pipework	Yes	No	No	No
organ stop	Yes	No	No	No

As nouns, organ stop is a hyponym of pipework; that is, organ stop is a word with a more specific, narrower meaning than pipework:

Other hyponyms of pipework include flue, flue pipe, labial pipe, reed pipe.

pipework (noun)	organ stop (noun)
the flues and stops on a pipe organ	a graduated set of organ pipes of like tone quality