As with all things, this is complicated, and your description is only one facet of the history of music in the church.

For instance, a major component of the Protestant Reformation was encouraging congregational singing, and (particularly Calvanist) church composers of the era brought the music of the church much closer to the contemporary "popular" music of the day.

The Protestant Reformation is exclusively a modern project. When I use the word ancient, I truly mean old. Much older than the high Middle Ages.

Given the fact that the Protestant Reformation encompasses roughly a quarter of the lifespan of the Christian church, I'm not sure it's fair to call it "exclusively modern".

Timespan is not as important as the shared perspective that defines modern religious thought, but even if it were, 25% is still far from a majority and, at least for most of that timeframe, Protestants were a small minority of Christians in the world (and they still are a minority).

I never claimed it was a "majority". My point is that the history of the Church is complicated, and Protestantism (representing roughly of a quarter of the catholic Church in terms of both time and people). Anything that encompasses 25-35% of a whole is significant enough to not be written off as "exclusively" anything.

How is that inconsistent with Christian theology? Theology is diverse and different schools hold different, often contradictory views on any given topic. Usually what is called “Christian theology” is that for which there is a general consensus among theologians, and I’m unaware of any such consensus on this particular subject.

In the year 2018, Christian theology is almost infinitely diverse, but it wasn't always so. That diversity is very modern. For the vast majority of Christian history, the sacramental role of music in Christianity was essentially a universal given. It wasn't until the Protestant Reformation that anyone even considered divorcing music from sacramental theology and it wasn't until the mid-20th century that the idea of church music as a matter of preference even arose. To speak authoritatively of "Christian theology" in the context of music in any meaningful sense, a "vote" needs to be given to every generation of Christians, not just the current one. And in that sense, there really is a consensus.

> To speak authoritatively of "Christian theology" in the context of music in any meaningful sense, a "vote" needs to be given to every generation of Christians, not just the current one.

Definitely, but we also need to consider that before the industrial revolution, Christians were limited in their options (most folks were very poor by modern standards, there isn't much diversity in music in general, and there is a comparatively narrow [and at various times, more corrupt] group of people making decisions on theology and music). So we need to consider history, but we don't weight all history evenly--there is such a thing as 'progress', after all.

> There is such a thing as 'progress', after all.

That's a bold claim that too many people accept without question and about which too few actually consider the implications.

Progress is improvement. It's moving forward. The notion requires accepting the idea that you were at one point behind where you are now or not as developed/complete/refined. That's fine if you are talking about technology or some other mundane topic, but to make that claim in the context of Christianity - a religion ENTIRELY dependent upon the veracity and completeness of the stories and traditions it is based upon - is to call into question the entire faith.

You've got it switched. Progress in the context of Christianity logically follows from the notion that some things are better/truer/holier than other things. If you can accept that anything has gotten better/truer/holier over time, then you believe in progress. Specifically, if you believe it's good that the Church is no longer teaching poor people that they have to pay for their family to go to heaven, then you believe in progress. If you don't believe in progress, then you don't believe in truth/goodness/holiness, then you are actually questioning the entire faith and we can't have a meaningful conversation.

By using something like indulgences as an example, you're making a false equivalency. It's certainly possible to call it progress if you are RECOVERING from a fall. You start high, dip down, progress back up to where you were. Indulgences did not exist in the early church and didn't even exist outside of the European church when they were a thing. In that context, the recovery of what was true was not progress, it was repair.

But to imply that from the BEGINNING Christians were incorrect on something as important as sacramental theology and the role of music in sacramental theology is a completely separate claim with severe implications, as I described above.

I don’t know what you mean by “from the beginning”, but in any case there is no existential faith crisis in rejecting even very early traditions or beliefs which were not part of scripture, as evidenced by the prolific success of Bible-focused denominations. The idea that hymns are the one true way to worship is utter nonsense.