"and I haven't been able to understand the relevance of that document."
That document expressed perfectly what was happening to the music in Ireland - it wasn't the opinion of a few old many, it articulated the attitude of the church and their desire to control Irish culture
Whenever the subject is discussed here in relation to what happened to the tradition, that is the one that is cited - Helen Brennan (a leading research figure in Irish dance, and Fintan Vallely both refer to it in their writings.
What happened to the music back then is very much a part of these discussions.
The music all but died then - it didn't die a natural death but was deliberately killed off and replaced by something else (controllable)
A similar thing happened in Scotland when the Church took against the tradition - there they drove the songs underground and ended up with a magnificent reprtoire of bawdy and erotic pieces.
Similarly in Wales, where the tradition was replaced by the outpourings from The Chapel
In your own country, go read the writings of White, Courlander and Lomax on how the preachers preached constantly about 'The Devil's Music'
All this is about control - mind and body.
I grew up surrounded by strong Catholic influences, but it wasn't until I started working in Ireland that I realised how deep these influences went in peoples lives literally, from before birth to after death
All forms of contraception were forbidden and women were encouraged to reproduce - no matter their financial or physical circumstances - having no children was, at best, a subject for sympathy, and at worst, a stigma.
The influences of baptism, church attendance, religious pressure at school, marriage.... what you could eat (especially on Friday)... are too well to re-open here, but a number of things were a total revelation to me.
I was introduced to 'Churching' by the 'Travellers' the idea that to give birth made a woman 'unclean', so much so that she was forbidden to prepare food in the home until, after a set period, she was 'Churched' (cleansed) by the priest by undergoing a set ritual
The saddest, and to me, the cruelest, were 'The Killeens'
Children who died after childbirth, before they could be blessed by the priest, were prohibited burial in consecrated ground and were consigned to the 'Killeens', often outside the local graveyard, but sometimes in a handy field set aside for the purpose.      
There are several in this area within a half hour's drive of our home
This is a description of 'The Angel's Plot in Glasnevin
"This Old Plot is the resting place for over fifty thousand infants who were buried there up to the 1970's. Glasnevin is one of the few Cemeteries that allowed stillborn babies to be buried in concentrated ground. In early times stillborn babies were not allowed in blessed ground, as they were unbaptised. Many babies were buried in the ditches and hedges on the outside of other cemeteries around the country. Often parents buried their babies themselves between dusk and dawn in fear of being caught and yet wanting their baby to buried in Holy Ground."
Cruel or what?
I sincerely believe that the Clerical abuses were a product of this desire to control
Jim Carroll