He graduated at the Budapest Liszt Academy of Music in 1982 studying in the class of Pál Kadosa.
During and after his studies he also undertook several master courses, such as the one led by György Cziffra in Senlis and Keszthely, too.
[3] István Kassai made CD recordings [4] of the complete piano works of Ernest Bloch, Ferenc Erkel, Mihály Mosonyi, Leó Weiner, Jenő Hubay and Sándor Balassa, which was followed by more than a dozen of CD releases including works by Ernő Dohnányi, Ferenc Liszt, Béla Bartók, Robert Volkmann, Imre Széchényi and Johannes Brahms.
At his concerts, he played the premieres or the first modern performances of numerous piano works i.e. pieces of Brahms and Bartók.
He has published numerous articles and studies on music and edited many volumes of sheet music by composers and musicians such as Liszt, Mosonyi, Hubay, Weiner and György Cziffra.