basset oboe vs heckelphone

basset oboe and heckelphone both are nouns.

Word	Noun	Adjective	Verb	Adverb
basset oboe	Yes	No	No	No
heckelphone	Yes	No	No	No

As nouns, basset oboe and heckelphone are synonyms defined as:

basset oboe and heckelphone: an oboe pitched an octave below the ordinary oboe

basset oboe (noun)	heckelphone (noun)
an oboe pitched an octave below the ordinary oboe	an oboe pitched an octave below the ordinary oboe