The Austrian Press Agency reported on Sunday that Harnoncourt had died surrounded by his family, after succumbing to a serious illness.

One of the most highly regarded classical music conductors of recent times, and a pioneer in early music, Harnoncourt had only announced his retirement in December.

At the time, the octogenarian had cancelled plans to conduct two concerts at the Musikverein by the Concentus Musicus, the ensemble he created in 1953.

Harnoncourt was born in Berlin in 1929 to a granddaughter of a Habsburg Archduke and an Austrian count, but he grew up in Graz, Austria.

A musical maverick

He trained as a cellist and embarked on intensive research into historical instruments and period performance, which led him to set up the Concentus Musicus. The ensemble began giving concerts in 1957 and specialized in renaissance and baroque music as well as classical works by the likes of Bach, Beethoven and Haydn.

Harnoncourt quit the Vienna Symphony Orchestra in 1969, after causing upset by his questioning of the established norms of the classical music scene.

His ideas eventually gained wider acceptance even in the mainstream, and now influence performances of older music by some of the world's greatest modern-instrument orchestras, including the Vienna and Berlin Philharmonics.