Phisycs and mechanics
The bandoneόn belongs to the family of free reeds and its mechanics is based on a few fundamentals:
- buttons or keys
On both sides, left and right, keys are arranged to form two keyboards, connected by bellows that can reach the remarkable width of about one metre.
The instrument has got 38 buttons for the medium-high register (right keyboard) and 33 buttons for the medium-deep register (left keyboard), its overall sound range covering about 5 octaves.
Not only do the two keyboards differ as to their extension and key layout, they also differ with regard to timbre: the right keyboard produces a bright, high-pitched sound, whereas the left one presents warmer, velvet nuances, offering a comprehensive and specific variety as to sound dynamics, timbre and articulation.
1. Left keyboard
2. Right Keyboard
Concerning mechanical details, every key is connected to a lever. By pressing a button, each lever will activate a small valve. Following the opening or closing of bellows, the valve will allow air to flow through, letting the two steel reeds – tuned in octaves – vibrate to produce a single sound. Compression and extension of bellows, in turn, are controlled by a lever set at the end of the right keyboard and activated by the thumb.
Both on the right and on the left sides, beneath each keyboard and inside the bellows, reeds are secured along six zinc plates, symmetrically placed onto three wooden parallelepipeds. Variations in the reed size correspond to different sounds, generated by the reed vibration: the wider and longer the reeds, the deeper the sound; the narrower and smaller the reeds, the higher the sound.
Unlike the accordion, where a chord is obtained by playing one key, the bandoneόn always requires several keys to be played at the same time to have a chord, just like on a piano keyboard, for instance.
From a performance viewpoint, the bandoneόn can be played either in a standing or a sitting position. The instrument is held by placing both hands through two leather straps fastened under the keyboards. Only the thumb is left free; on the right hand, it has the chief task to control the valve allowing to open and close the bellows.