What is a Hymn?
Author: Mrs. Myriam Van Lerberghe-Thibaut
The are many sorts of Gregorian chants: Tract, Sequence, Canticle, Hymn, etcetera. Here is some explanation on the Hymn, because the Rorate coeli is a Hymn.
A Hymn is a chant with lyrics not originating from the Bible. Precisely because it is not a biblical text, there was plenty of room for experimenting with lyrics and music. The words are always in a fixed pattern of metrical foots, often pedantic, mostly rhymed and because of that often linguistically complex and hard to understand.
For what pertains to the musical form the Hymn is stanza song: a fixed tune for several stanzas, with a refrain in between. The tune is not that tightly linked to the words als in "common" Gregorian chants, where the music closely follows the emotions of the words (e.g. Beati mundo corde were the music follows the words excellently).
Why is the Hymn Rorate coeli not present in our Graduale Romanum?
In our GR only the chants linked with the Liturgy of the Mass are present. The home of Rorate coeli is the Evening Office of advent, not the Mass. Other Hymns are linked to the Mass, e.g. Te Deum and Veni Creator. So there is no general rule.
Our commentators: