The accordion is a small, portable box-shaped instrument with metal reeds, which vibrate as air, distributed by a bellows, flows across them. The principle of sound production on the accordion is the same as the harmonica, the difference being that the former is equipped with a bellows and keys that produce the desired tones. Just like the piano, the accordion is a keyboard instrument with a range of 3 ½ octaves. It is designed to be held in both hands, which move towards or away from each other, compressing or expanding the bellows. The keys or buttons that produce the melody are played with the fingers of the right hand, while the buttons that produce simple chords for accompaniment are controlled by the left hand. Damian of Vienna is credited with inventing the accordion.

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The Harmonium is an electric musical keyboard instrument on the twelve-tone scale, and was developed as a portable alternative to the classic church organ, which was permanently installed in churches and places of worship, due to its very large size. The harmonium stands out for its capacity to produce a wide range of timbres (folk musicians call them “registra”), combining different harmonic sound frequencies that create consonances. It is thought to have been invented in Paris, in 1842, by Alexandre Debain; the electric version appeared in the mid-1930s (e.g. Hammond B3). Since the 1970s, the harmonium gradually began to give way to synthesizers, which can produce an even broader range of timbres.