air moving ("whooshing"), which is sometimes used in contemporary compositions for this instrument Body The accordion's body consists of two boxes, commonly made of wood, joined by the bellows. These boxes house reed chambers for the right- and left-hand manuals. Each side has grilles in order to facilitate the transmission of air in and out of the instrument, and to allow the sound to project. The grille for the right-hand manual is usually larger and is often shaped for decorative purposes. The right-hand manual is normally used for playing the melody and the left-hand manual for playing the accompaniment; however, skilled players can reverse these roles and play melodies with the left hand. The size and weight of an accordion varies depending on its type, layout and playing range, which can be as small as to have only one or two rows of basses and a single octave on the right-hand manual, to the most common 120-bass accordion and through to large and heavy 160-bass free-bass converter models. Pallet mechanism The accordion is an aerophone. The manual mechanism of the instrument either enables the air flow, or disables it: Variable components The term accordion covers a wide range of instruments, with varying components. All instruments have reed ranks of some format, apart from reedless digital accordions. Not all have switches to change registers or ranks, as some have only one treble register and one bass register. The most typical accordion is the piano accordion, which is used for many musical genres. Another type of accordion is the button accordion, which is used in musical traditions including Cajun, Conjunto and Tejano music, Swiss and Slovenian-Austro-German Alpine music, and Argentinian tango music. The Helikon-style accordion has multiple flared horns projecting out of the left side to strengthen the bass tone. The word "Helikon" refers to a deep-pitched tuba. Right-hand manual systems Different systems exist for the right-hand manual of an accordion, which is normally used for playing the melody (while it can also play chords). Some use a button layout arranged in one way or another, while others use a piano-style keyboard. Each system has different claimed benefits by those who prefer it. They are also used to define one accordion or another as a different "type": Chromatic button accordions and the bayan, a Russian variant, use a buttonboard where notes are arranged chromatically. Two major systems exist, referred to as the