mouth harp vs mouth organ

mouth harp and mouth organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
mouth harp	Yes	No	No	No
mouth organ	Yes	No	No	No

As nouns, mouth harp and mouth organ are synonyms defined as:

mouth harp and mouth organ: a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole

Other synonyms of mouth harp include harmonica, harp.

mouth harp (noun)	mouth organ (noun)
a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole	a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole