Free reed aerophone in the context of "Breath"

Accordions (from 19th-century German Akkordeon, from Akkord—"musical chord, concord of sounds") are a family of box-shaped musical instruments of the bellows-driven free reed aerophone type (producing sound as air flows past a reed in a frame). The essential characteristic of the accordion is to combine in one instrument a melody section, also called the diskant, usually on the right-hand keyboard, with an accompaniment or Basso continuo functionality on the left-hand. The musician normally plays the melody on buttons or keys on the right-hand side (referred to as the keyboard or sometimes the manual), and the accompaniment on bass or pre-set chord buttons on the left-hand side. A person who plays the accordion is called an accordionist.

The accordion belongs to the free-reed aerophone family. Other instruments in this family include the concertina, harmonica, and bandoneon. The concertina and bandoneon do not have the melody–accompaniment duality. The harmoneon is also related and, while having the descant vs. melody dualism, tries to make it less pronounced. The harmonium and American reed organ are in the same family, but are typically larger than an accordion and sit on a surface or the floor.

The harmonica, also known as a French harp or mouth organ, is a free reed wind instrument used worldwide in many musical genres, notably in blues, American folk music, classical music, jazz, country, and rock. The many types of harmonica include diatonic, chromatic, tremolo, octave, orchestral, and bass versions. The harmonica is played by using the lips and tongue to direct air into or out of one (or more) holes along a mouthpiece (which covers one edge of the harmonica for most of its length). Behind each hole is a chamber containing at least one reed. The most common type of harmonica is a diatonic Richter-tuned instrument with ten air passages and twenty reeds, often called a blues harp. The harmonica reed is a flat, elongated spring typically made of brass, stainless steel, or bronze, which is secured at one end over a slot that serves as an airway. When the free end is made to vibrate by the player's air, the reed alternately blocks and unblocks the airway to produce sound.

Reeds are tuned to individual pitches. Tuning may involve changing a reed's length, how heavy it is near its free end, or how stiff it is near its fixed end. Reeds that are longer, heavier, or more flexible produce lower pitches; shorter, lighter, or stiffer reeds produce higher pitches. If, as on most modern harmonicas, a reed is affixed above or below its slot rather than in the plane of the slot, it responds more easily to air flowing in the direction that initially would push it into the slot, i.e., as a closing reed. This difference in response to air direction makes it possible to include both a blow reed and a draw reed in the same air chamber, and to play them separately without relying on flaps of plastic or leather (valves, wind-savers) to block the nonplaying reed.

The pump organ or reed organ is a type of organ that uses free reeds to generate sound, with air passing over vibrating thin metal strips mounted in a frame. Types include the pressure-based harmonium, the suction reed organ (which employs a vacuum system), and the Indian harmonium. Historical examples include the Kunstharmonium and the American reed organ, while earlier forms include the physharmonica and the seraphine.

More portable than pipe organs, free-reed organs became widespread in smaller churches and private homes during the 19th century, although their volume and tonal range were limited. They generally featured one, or occasionally two, manuals, while pedal-boards were rare. Higher-end pump organs offered a broader range of tones, and models intended for churches or affluent households were often housed in finely crafted cabinets.

The Harmoneon or concert accordion (French: Harmonéon, accordeon de concert) is a French free reed aerophone, invented by Pierre Monichon in 1948, although he only patented the instrument four years later in 1952. It has been taught in musical conservatories since 1974. The instrument has great similarity to both the duet concertina and button accordion.

The melodica is a handheld free reed instrument similar in sound to a pump organ or harmonica. It features a musical keyboard on top, and is played by blowing air through a mouthpiece that fits into a hole in the side of the instrument. The keyboard usually covers two or three octaves. Melodicas are small, lightweight, and portable, and many are designed for children to play. They are popular in music education programs, especially in Asia. The modern form of the instrument was invented by Hohner in the late 1950s, though similar instruments have been known in Italy since the 19th century.