El Canto de la Sibila in Majorca

The song is sung by a young man (with no instruments, except the organ), who is accompanied by at least two altar boys, although people of all generations take part in the ritual to guarantee it is passed on. It is a living example of medieval religious folklore.

The Song of the Sibyl is a liturgical drama of Gregorian melody. Before Christmas Eve, a child disguised as a woman (a representation of the Erythrean Sibyl, a personage of classical mythology who predicted the end of the world) is placed wielding a sword, very theatrical, in the steps of the high altar, where he sings, with the beauty of Gregorian chant and the magic of children's voices, a series of verses on the Last Judgment, intercalating them with the refrain 'Strong Judgment give us God'.

At the moment it is still sung in the churches of Majorca during Misa del Gallo in the cathedral of Palma and the Monastery of Lluc. It is also performed in other places, like the cathedral of Toledo, in which they are trying to recover the custom in recent years.

If you want to see this in person, you can stay in La Victoria Hostel.

Source: http://www.spain.info/es/que-quieres/agenda/fiestas/mallorca/canto-de-la-sibila.html