free-reed vs reed instrument

free-reed and reed instrument both are nouns.

Word	Noun	Adjective	Verb	Adverb
free-reed	Yes	No	No	No
reed instrument	Yes	No	No	No

As nouns, reed instrument is a hypernym of free-reed; that is, reed instrument is a word with a broader meaning than free-reed:

free-reed: a reed that does not fit closely over the aperture
reed instrument: a musical instrument that sounds by means of a vibrating reed

Other hypernyms of free-reed include beating-reed instrument, reed.

free-reed (noun)	reed instrument (noun)
a reed that does not fit closely over the aperture	a musical instrument that sounds by means of a vibrating reed