Dies Irae (Day of Wrath)
Dies Irae is a 13th Century poem which describes the day of judgment, the last trumpet summoning souls before the throne of God, where the saved will be delivered and the unsaved cast into eternal flames. The hymn Dies Irae is best known from its use as a sequence in the Roman Catholic Requiem mass (Mass for the Dead or Funeral Mass). Below is a recording of how it would have sounded in the 13th Century, chanted by monks.
Look up various Dies iraes on youtube to get the idea of how the interpretation changed over the centuries. (Saint-Sains, Verdi, Mozart, Fauré, Karl Jenkins). This is Raymond Deane's versiono DiesIrae.
This section is characterised by unusual intervals, (e.g. minor 2nds), dissonance (clashy chords), a canon between marimba and violin and use of prime numbers on guiro.