Considered one of the most important choral conductors of the postwar period, Gillesberger began his formal studies in both church music and jurisprudence in Innsbruck and in Vienna. Gillesberger was the musical director of the Vienna Boy's Choir from 1942 to 1945. He then was engaged in the position of deputy director of the choir for the Vienna State Opera. In 1961, he became a professor at the Wiener Musikhochschule (Vienna Academy of Music) and in 1965, he was again associated with the Wiener Sängerknaben (Vienna Boy's Choir), in the position of artistic director. His recorded work focuses especially on the works of J.S. Bach; the Classical period works of Franz Josef Haydn and W.A. Mozart; and the Romantic era expressed through the compositions of Franz Schubert, Franz Liszt, and Anton Bruckner.