János Sebestyén's formal musical education began in 1946 at the State Music Secondary School as a student of pianist István Antal, organist János Hammerschlag, and composer Ervin Major. He continued his studies with Ferenc Gergely at the Academy of Music and graduated there with an organ diploma in 1955. As organ and harpsichord soloist he performed throughout Europe, Asia and the United States, and made more than eighty recordings for a number of international labels. In 1970 he established the harpsichord class at the Academy of Music where he was professor until 2009.
From 1950 he was a prominent figure at Hungarian Radio, contributing hundreds of programs documenting nearly every aspect of culture and politics during the last century. He also appeared regularly on Hungarian television, famously hosting the annual New Year's concert from Vienna for thirty-five years. His publications include Stories From My Life
(1980), a biography of composer Miklós Rózsa compiled from taped interviews, and Those Radio Years
(1995), a history of Hungarian Radio co-authored with Jenő Randé. He served as President of the Jury for the International Liszt Organ Competition in 1983, 1988 and 1993, and in 2000 for the First International Harpsichord Competition, Budapest.
His awards in Hungary include the Erkel Prize (1967), Liszt Prize (1974) and the title Artist of Merit (1982). In August 2000 he was awarded the Officer's Cross by Hungarian president Ferenc Mádl in recognition of fifty years of service to Hungarian Radio. International awards include the title Cavalier of the Italian Republic (1984), the Portuguese title Grande Comendador of the Henrique Infante State Order (1996) and in 1999 he was awarded the rank of Officer in the Isabella la Católica Order by King Juan Carlos I of Spain. In February 2000 he was awarded the title Cavalier of the Order of the Southern Cross by the Brazilian government, and in December that same year he was appointed Officer in the Royal Order of the Nordic Star by King Carl XVI Gustaf of Sweden. In recognition of his artistic achievements and commitment to Italian culture, he was awarded the title Official of the Italian Republic in November 2003.