Integrated by the Spanish flutist Marta Femenía and the Cuban pianist Karla Martínez, started their musical activity in the Ciclo Preludio of the Reina Sofía School in 2016, being both students of the mentioned institution. They belong to the Grupo Danzi, (currently Brises Ensemble), quintet of winds and piano awarded with the most outstanding ensemble Diploma in Chamber Music in 2016, received from Her Majesty Queen Sofía.     

One of their main influences has been the work in the Chamber Music lessons with the pianist and professor Márta Gulyas and with the remarkable professors Klaus Thunemann, Hansjörg Schelenberger and recently with Davide Formisano.

In 2016 they were selected to participate in the cycle Clásicos en ruta of the AIE for the 2016-17 season with the name of Dúo Femenía-Martínez, where they presented a complete repertory that included works of different styles and that had as a distinctive and essential element the inclusion of Spanish contemporaneous works. From 2018 they change the name to Dúo Ópalus and for the 2017-18 season they take part of the catalogue of artists of Juventudes Musicales de España presenting a repertory with great technical and stylistic complexity with works from baroque to nowadays. They performed throughout all the Spanish territory, in places like Madrid, Sevilla, Cádiz, Ciudad Real, Lugo, Mérida, Alcalá de Henares, Ponferrada, Pamplona, Gijón, Sober, San Cugat, Calahorra, Ávila y Valladolid. Their most recent performances have been in Bratislava (Slovakia) and Germany.