The bass baritone, Robert Koller, has many years of experience in the concert and opera world. He has performed in prestigious opera houses and concert halls such as "Alte Oper Frankfurt", Zellerbach Hall/San Franciso, Semperoper Dresden, Philharmonie Berlin and the Teatro Colon in Buenos Aires, under various conductors like Andrea Marcon, Heinz Holliger, Jordi Savall, Emilio Pomárico and Christian Schumann.

Since 2004, he has been singing the role of King Cosroe in "Siroe, Re di Persia" by Haendel with the Venice Baroque Orchestra, under the direction of Andrea Marcon at the Musikhalle Hamburg and at the Zellerbach Hall, San Francisco. This has led to his soloist appearances in various works by Charpentier with the Capella Reial de Catalunya under Jordi Savall at the Styriarte Graz and the festival of Ambronay and the Basilica of Vézelay.

He has performed a broad range of leading roles and recitals in renowned theatres and festivals including the Società di Quartetto Milano, the Summer Concerts of the Audi-Forum Ingolstadt, the Teatro Principal de Guanajuato as part of the Cervantino Festival Mexico, the Ruhr-Triennale, the Festival of Montepulciano, the Davos-Festival, the Gaida Festival Vilnius and the Lucerne Festival with the Lucerne Festival Strings at the KKL.

Swiss radio broadcasted his solo performances with leading Swiss orchestras such as the Orchestre de Chambre de Lausanne, the Kammerorchester Basel, the Kollegium Musicum Winterthur, the Basel Sinfonietta (at the Stadtcasino Basel), the Ensemble Phoenix or the Contrechamps Genève.

He was the leading role in "Extravagancia" at the Teatro Colón in Buenos Aires...