A requiem Mass, for the repose of the soul of the deceased. Black vestments are worn, for obvious reasons, also usually there is no communion. ( may vary in some areas)
The original purpose is to have it sung in memory of the dead. Sometimes, though, it is sung just because people like the music. By the way, there are many different musical settings for the requiem mass. The Gregorian chant requiem has been used by the Catholic church for centuries. Composers such as Mozart and Verdi wrote later settings.
A nuptial mass is one celebrating a wedding. A requiem mass is one to honor someone who has died.
Requiem duhhh
If you're asking what type of musical composition honors the dead, that would be a Requiem, or Requiem mass. This music is the most common at funerals but not exclusive to them. They are religious vocal works usually sung in latin that have distinct ties to Medieval Gregorian Chant. A popular composer at the time who composed a Requiem would be Verdi and also Mozart (though he ironically died before completing his requiem).
The mournful requiem echoed through the halls of the cathedral, filling the air with a sense of solemnity and sadness.
a musical composition used in a mass for the dead
In the Catholic church, the Mass for the dead was previously know as a Requiem Mass, and all of the rites surrounding that were referred to as a "Requiem". Exequy
Agnus Dei, referring to the Christian theological concept the Lamb of God, and the associated liturgical text from the Roman Catholic Latin Mass has been set to music by many composers, as it is normally one of the movements or sections in a sung Mass setting or Requiem Mass.
they were both sung in the language of the audience
Mozart's Mass Requiem.
Requiem Mass