Watch Full Movie Online. 'El sonido del bandoneon' is a documentary film about the instrument that is most associated with passion: the bandoneon. The film is a search for the soul and special sound of this magical instrument that is so inextricably linked to Argentina and its most famous musical expression, the tango.The story of the bandoneon now seems to be headed for a dramatic ending. The old bandoneons from the beginning of the 20th century break down or are bought by collectors, and new bandoneons are made only in very small quantities. These new bandoneons lack the quality and special sound of the German originals and are expensive. So there are fewer bandoneons around, the once so popular instrument is played by fewer musicians, ad the bandoneon is in very real danger of disappearing altogether.