(OEIN, Experimental Orchestra of Indigenous Instruments) is a unique contemporary music ensemble. It works with traditional instruments of the Andes which, while also bearing profound cultural significance, constitute a vast source for the exploration of sound.
The idea behind the OEIN is to bring ancient pre-Colombian roots of the Andes into the present times, recognising their value while importantly taking on the challenge of creativity into a contemporary proposal.
While the OEIN principally performs new music specially created for this ensemble, its repertoire is diverse and includes ancient music of the Andean communities. The musical foundation of the ensemble is twofold: traditional music constitutes the basis of its techniques and philosophy, whereas new music serves as its medium of expression and represents the identity of our times.
It is important to note that in the OEIN’s repertoire, the instruments are incorporated into the music as originally built, with their own traditional blowing techniques, nontempered tuning, and characteristic performer behaviour.
The OEIN is also an educational program on music initiation, based on philosophical principles, originating in and reflecting the Andean way of thinking. All members of the OEIN are former students of this educational programme, which reaches 500 children and youths every year in La Paz.
Musicians at the OEIN are able to play the entire range of native instruments and can consequently group or divide themselves according to the requirements of each musical work (as opposed to the formal division into instrumental sections as is customary in conventional orchestras).
In addition, the OEIN has developed a residence program in order to stimulate new music creation among young composers, mostly from Bolivia, but also from Argentina, Brazil, Uruguay, Ecuador, Costa Rica, and even Switzerland and Austria. Thanks to this programme, the OEIN’s repertoire has increased significantly and has broadened its acoustics and aesthetics.
The OEIN was founded in 1980. Since then, it has developed an exclusive repertoire of new music composed especially for this ensemble.
The OEIN has issued five recordings on the Cantvs label, Bolivia. The ensemble’s interpretations have been featured on other CDs (Tacuabé, Uruguay 1981; SECAB Sony Music, Colombia 1996). In addition, the OEIN has made live recordings for Swiss Radio, German Radio, South West German Radio, ORF (Austria).
Internationally, the OEIN has performed in Donaueschinger Musiktage, Neue Musik Rümlingen in Switzerland, Musikakademie in Basel, Klangspuren (2009–11), Transart (2009–11), Experimenta (Argentina), Núcleo Música Nueva (Uruguay), and Músicas del Mundo (Colombia). Chamber sections of the OEIN have performed at the Perth Festival, Klangzeit Münster, P’iri (Korea), Instrumenta (Mexico), Ciclo Ópera Contemporánea (Argentina).
Within its residency programme, the OEIN has worked with leading international composers such as Graciela Paraskevaídis, Tato Taborda, Alejandro Cardona, Mesías Maiguashca, Beat Furrer, Mischa Käser, who have written music especially for the ensemble. This experience has also included Bolivian composers of the young generation, such as Carlos Gutiérrez, Daniel Calderón, Carlos Nina, Canela Palacios, Miguel Llanque, Lluvia Bustos, and many others.
The OEIN has cooperated with institutions such as Prince Claus Fund, Pro Helvetia Foundation, South West German Radio, Goethe-Institut, Klangspuren and TransArt festivals, CAF (Corporación Andina de Fomento), IBD, the Bolivian Minister of Education, and the City of La Paz.
The EOIN explores the musical instruments of the Aymaran culture from the Bolivian highlands, organised into unique structure called tropas (troops) as a collective idea of sound. A tropa can be defined as an ensemble of instruments belonging to a single organological family consisting of different registers or sizes (varying from one to six), each doubled and expanded as required by the ancient criteria of integrated sound. Tropa is, therefore, a physical unity that shapes the cooperative unity of musicians in the act of music making.
The tropa is formed of couples, structured according to another ancestral principle named arca-ira: ira (the one that comes in front) and arca (the one that follows from behind). In playing, each musician complements the notes of the other, and by alternating their notes, both musicians build a musical flow that reinforces the dual unity. This concept is further applied to different kinds of instruments like panpipes, notched flutes, vertical flutes, transverse flutes, and in consequence, establishes a reciprocity and duplication between the registers of the tropa.

Cergio Prudencio La Paz, May 2009