helicon vs bombardon

helicon and bombardon both are nouns.

Word	Noun	Adjective	Verb	Adverb
helicon	Yes	No	No	No
bombardon	Yes	No	No	No

As nouns, helicon and bombardon are synonyms defined as:

helicon and bombardon: a tuba that coils over the shoulder of the musician

helicon (noun)	bombardon (noun)
a tuba that coils over the shoulder of the musician	a large shawm; the bass member of the shawm family
	a tuba that coils over the shoulder of the musician