The Loreto bells will play a traditional Christmas melody from December 24 till February 2. It is the first time in over 120 years.
The melody – which is a closely guarded secret – will sound every hour from 10:00 to 17:00 daily.
The Christmas carol was last heard at the end of the 19th century when the melodies in the mechanism changed regularly. It was designed so as to allow a change of melody fairly easily.
The Loreto (Loreta) was built during the 17th century (1626) at the order of Katerina of Lobkowicz, in the times of Ferdinand II, as part of the Catholic campaign to attract the Czechs back to Catholicism.
Its construction followed the battle of the White Mountain, where the Czech Protestants were defected and the Catholics retook control over Prague.
Its impressive Baroque Bell Tower was given to the Loreto by the rich merchant from the Lesser Town, Eberhard von Glauchau.
The author of all twenty-seven signed playing bells (only one was damaged in the 18th century and replaced) was the Amsterdam town bell-founder Claude Fremy, who made them between 1683-91.
The consecration of the bells in the Loreto in 1695 before they were set in the clock-tower was a grand occasion. Every bell had its sponsor from among the ranks of the high aristocracy; Emperor Leopold I assumed patronage of the first of them.