Accordions refer to a family of box-shaped musical instruments of the bellows-driven free-reed aerophone type, colloquially referred to as a squeezebox. (source: wikipedia)
This definition is highly relevant because it highlights a number of key aspects:
The accordion family includes an array of different instruments (e.g. concertina, bandoneon, harmonium, American reed organ), with the accordion alone consisting of several types (e.g. chromatic, diatonic, standard or free bass)
- The accordion is polyphonic in many ways. It allows several notes to be played at once, not only by pressing several keys, but also by pressing only one key (with pre-set chords on the left hand, and the use of multiple voices simultaneously). It is therefore highly polyphonic, which makes it an excellent one-man band instrument.
- The accordion is a free reed aerophone.
- The accordion is an expressive instrument. As the motion of its bellows makes air pressure vary, the musician can express nuances, unlike other parent instruments, such as the organ.