Early life and education
Demus was born in St. Pölten; his father was an art historian and his mother a concert violinist. At the age of six, Demus received his first piano lessons. Five years later, at the age of 11, he entered the Vienna Academy of Music, studying piano, composition and conducting. He made his debut as a pianist when he was still a student: at the age of 15, he played in the Brahms-Saal of the prestigious Gesellschaft der Musikfreunde Bach's Das wohltemperierte Klavier. He graduated in 1945, then 17 years old, after which he continued to study conducting with Josef Krips and Hans Swarowsky. Demus studied in Paris with Yves Nat from 1951 to 1953. In 1953 he further studied interpretation with Wilhelm Kempff, Arturo Benedetti Michelangeli, and Edwin Fischer, and attended master classes with Walter Gieseking.