An instrument, also called the "mouth organ", which consists of reeds in a casing which channel the air blown into the instrument through channels and out holes on the side of the instrument. The harmonica was invented in 1821 and is used mostly in folk music.
See also [Eng.] harmonica; [Eng.] mouth organ; [Fr.] harmonica (f); [Ger.] Mundharmonika (f); [It.] armonica a bocca (f).
Photo courtesy of Lark In The Morning