concert grand vs concert piano

concert grand and concert piano both are nouns.

Word	Noun	Adjective	Verb	Adverb
concert grand	Yes	No	No	No
concert piano	Yes	No	No	No

As nouns, concert grand and concert piano are synonyms defined as:

concert grand and concert piano: a grand piano suitable for concert performances

concert grand (noun)	concert piano (noun)
a grand piano suitable for concert performances	a grand piano suitable for concert performances