parlour grand piano vs parlor grand

parlour grand piano and parlor grand both are nouns.

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

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

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

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