baby grand piano vs parlour grand piano

baby grand piano and parlour grand piano both are nouns.

Word	Noun	Adjective	Verb	Adverb
baby grand piano	Yes	No	No	No
parlour grand piano	Yes	No	No	No

As nouns, baby grand piano and parlour grand piano are synonyms defined as:

Other synonyms of baby grand piano include baby grand, parlor grand, parlor grand piano, parlour grand.

baby grand piano (noun)	parlour grand piano (noun)
a small grand piano	a small grand piano