A visitor views the special exhibition of the "Triad of the first Viennese school: HAYDN-MOZART-BEETHOVEN" in Mozart house museum, Vienna, Austria, Feb 19, 2020. The exhibition, part of a series of events marking the 250th anniversary of Beethoven's birth, is held from Feb 19, 2020 to Jan 31, 2021. (GUO CHEN / XINHUA)

A visitor views the special exhibition of the "Triad of the first Viennese school: HAYDN-MOZART-BEETHOVEN" in Mozart house museum, Vienna, Austria, Feb 19, 2020. (GUO CHEN / XINHUA)

A visitor views the special exhibition of the "Triad of the first Viennese school: HAYDN-MOZART-BEETHOVEN" in Mozart house museum, Vienna, Austria, Feb 19, 2020. (GUO CHEN / XINHUA)

A visitor views the special exhibition of the "Triad of the first Viennese school: HAYDN-MOZART-BEETHOVEN" in Mozart house museum, Vienna, Austria, Feb 19, 2020. (GUO CHEN / XINHUA)

Exhibits are seen during the special exhibition of the "Triad of the first Viennese school: HAYDN-MOZART-BEETHOVEN" in Mozart house museum, Vienna, Austria, Feb 19, 2020. (GUO CHEN / XINHUA)