The accordion is an instrument that can be difficult to classify. Technically, it is a type of aerophone. However, it can also be classified into progressively smaller subgroups of instruments. The instrument's more specific classifications provide additional clarification on its role and instrument family. While it is tempting to classify this instrument as a keyboard instrument, that is incorrect, since the process of producing sound involves wind and the keyboard by itself does not produce the sound.
Aerophones are wind instruments. In order for an instrument to be considered a wind instrument, the primary method of producing sound has to involve sending air through the instrument. There are various ways of producing the air, but as long as the instrument relies on airflow to produce sound it can safely be considered an aerophone. The accordion is considered an aerophone because of its use of wind to produce the sound. Other aerophones include the reed organ and harmonica, as well as several others.
Aerophones can be further classified as free or pipe aerophones. Pipe aerophones determine pitch by the length of the pipe. Longer pipes will produce lower pitches, while shorter pipes will produce higher pitches. Trumpets and trombones are examples of pipe aerophones. The accordion is a free aerophone since the pipes exist only to transmit air and do not affect the pitch of the instrument. Rather, the pitch is affected by a system of buttons on the side of the accordion that directs the airflow over different sized reeds.
Reed instruments can be either free read or beating reed instruments. Free reed instruments let the reeds vibrate freely. This makes the accordion a free reed instrument since the reed does not bang against another object. The beating reed instruments have reeds that beat against something to produce a sound. The vocal folds of the human voice are considered to be a beating reed instrument; so are the organ and bassoon. In addition, there are framed and unframed reeds. The accordion falls into the category of unframed reeds since it does not rely on a metal brace to "frame" the reed.
The final category includes the manner in which the instrument is blown. As mentioned previously, aerophones use air to produce sound. The manner in which sound is produced is crucial to a proper classification. Air can be produced mechanically, with the mouth, the hand or the foot. In the case of the accordion, the hand creates the airflow, since the accordion is opened and closed with the hands while playing. This makes the accordion a hand-blown, free, unframed reed aerophone.