|Memling Judgment Day - 1460|
Now that a charmer of a warming-upper. Growing up in performance, big deal churches often put on a requiem either today (Good Friday) or Easter Sunday. After a year's diet of mediocre church music, this was a weekend when Brahms, Mozart, or Verdi showed up and the challenges of difficult and famous music came with them.
The Mass for the Dead draws from "ordinaries and propers". Ordinaries are the parts that "ordinarily" show up - Introit, Gloria, Credo etc.. Propers are specific to a day in the church year. The Dies Irae appears in Requiems because for the dead person, it is judgment time - up or down so to speak.
Contemplation of the Dead 1895