Harmonica is a small wind instrument (English Harmonica), blown or inhaled by the mouth, the metal reed vibration sound multi-reed instrument; A wind instrument that belongs to a free spring in the classification of Musical Instruments. The sound source is a reed between 1.5 and 3.5cm in length rather than an air column. Harmonicas are mainly divided into solo harmonicas and ensemble harmonicas, each of which has different types. Its range varies slightly according to different types and tonality. As a melodic instrument, the harmonica can play at least two chords, and advanced players can play two relatively independent parts at the same time while following the harmonica structure. It is called the "piano in your pocket" because of its small size.