gymel vs polyphony

gymel and polyphony both are nouns.

Word	Noun	Adjective	Verb	Adverb
gymel	Yes	No	No	No
polyphony	Yes	No	No	No

As nouns, polyphony is a hypernym of gymel; that is, polyphony is a word with a broader meaning than gymel:

gymel: the technique, found in some medieval English music, of singing voice parts in parallel thirds.
polyphony: music arranged in parts for several voices or instruments

Other hypernyms of gymel include concerted music, polyphonic music.

gymel (noun)	polyphony (noun)
the technique, found in some medieval English music, of singing voice parts in parallel thirds.	music arranged in parts for several voices or instruments