The Blue Danube is traditionally played at midnight during Vienna's City Hall Square New Year's Eve celebration.
The piece is a waltz by Johann Strauss II, formally titled “On the Beautiful Blue Danube.” It was first performed in 1867 and became one of the composer's best-known works. Its flowing triple-meter rhythm made it an enduring symbol of Viennese musical culture.
In Vienna, the melody is heard at midnight during public New Year's celebrations and is also broadcast nationally. Audiences commonly join in with applause and dancing after the final chimes. The piece is often confused with the “Radetzky March,” another Strauss-family work that is strongly associated with the New Year's Concert.
The Vienna Philharmonic's famous New Year's Concert is a separate event held on New Year's Day, not the midnight street celebration. It traditionally includes music by the Strauss family and ends with the “Radetzky March,” which explains the frequent mix-up.