What is the meaning of "The Gathering" in Gathering Blue.

In Chapter Three of this excellent dystopian classic we
are introduced to "The Gathering," which we are told happens once a year and is when the
Singer, an important person in the community, sings The Ruin Song, which is a narrative
song that tells the people the history of mankind over the
years:

The
Ruin Song was lengthy and exhausting. It began with the beginning of time, telling the
entire story of the people over countless centuries. It was frightening too. The story
of the past was filled with warfare and disasters. Most especially if was frightening
when it recalled the Ruin, the end of the civlisation of the
ancestors.

Singing the Ruin
Song is the only job of the Singer, and, because of the length of the song, we are told
that he takes lots of time to prepare and has to rest his voice for days before the
Gathering. It is required for everyone to attend the Gathering and hear the Ruin Song,
perhaps so that the history of mankind can be remembered by all and that mistakes are
not repeated. Elsewhere we are told that reading and writing is only taught to a select
few, so the Ruin Song is a verbal narration of history that can be listened to and
remembered by all of the community.