Th e purpose of this article is to show the need of musical study of "Sonsureño", a popular rhythm from Nariño Department andean region.Th e ethnomusical principles and proposals of the Hungarian composer Béla Bartók, have served as a reference framework to achieve the present paper.By means of his comparative procedures we have been able to get to some conclusions which allow us to establish a conceptual basis useful to bring up an academic discussion as far as this musical phenomenon is concerned.Two points related to this rhythm are analyzed: on one hand, its presence in the rural and urban music and, on the other, its arrival to academic music, which has been put in evidence in the music of nariñense composer Javier Fajardo Chaves.Taking into account these two topics, some terms are defi ned and the object of the study is limited to a specifi c musical fi eld putting it apart, in this way, from the merely speculative plan in which it has been immersed.Th ree variants are considered as giving it its rich sonority: Ecuadorian Andes, Colombian Andes and Pacifi c Coast, originating in this way certain ambiguities in its rhythm and accompaniment.