István Viszló is a member of the Hungarian National Choir, as well as a section leader and voice coach there. He earned his degrees in Pécs and Miskolc under the guidance of Katalin Schultz, Atilla Kiss B. and Bernadett Wiedemann.
He has also belonged to such ensembles as the Honvéd Male Choir, the Budapest Tomkins Vocal Ensemble, the Cantus Corvinus Vocal Ensemble, and was a founding member of the Saint Ephraim Male Choir. Also a permanent soloist with the Saint Ladislaus Choir of Kőbánya, he has appeared in numerous oratorios and composer's recitals. His repertoire ranges from the Baroque era to contemporary music.