The melodica is a free-reed instrument which operates reeds in a similar way to the harmonica. It has a musical keyboard on top (usually 2-3 octaves) and is played by blowing air through a mouthpiece/pipe that fits into the side of the instrument; pressing a key allows air to pass through the reeds. Single notes and chords can be played on the melodica's keyboard.
Melodicas are small, light, and portable and popular in music education. Unlike most woodwind instruments, they make use of a piano keyboard so the melodica player uses one finger to play any note on the instrument, rather than requiring several fingers to play individual notes as required for other woodwind instruments e.g flute, clarinets etc. The melodica can also play accidental notes more easily than other woodwind, which require extra keys or cross-fingering to reach any notes outside of the instruments natural key. These two factors give the melodica an unusual degree of flexibility and contribute to its wide usage in music education.
The melodica has been around since the 1950's and was first used as a serious musical instrument in the 1960s and can now be found being used in jazz, contemporary, reggae, and many other music types.
The melodica is also known by numerous other names e.g. blow-organ, key-flute, melodia, melodihorn, melodika, melodion and pianica!!