I'm writing this on here because it would be too long even for a multiple Tweet thread.
I am an atheist. This means that, having thought about the matter for many years and weighed up the evidence, I find it highly unlikely that a supernatural being called God exists. To find out my reasons, it's worth reading Christopher Hitchens' God is Not Great, which by-and-large articulates, in a hugely entertaining way, the conclusions I had already drawn.
Some bloke appeared on Radio 4's ghastly Thought for the Day slot and said he found it impossible that people who don't believe in God could appreciate music. I wondered if it was possible to get any more patronising, rude or stupid, whilst clearly talking with a smug grin on his face.
It is pertinent to ask, however, how people who don't believe in a christian god can appreciate 'Sacred Music'. I could be chippy and say it's because we have very broad minds. But that isn't necessarily the case.
Years ago I bought a two volume chronological anthology of English poetry, and was horrified to find that every single poem in volume one was about, or to, the Christian God. Were these people obsessed by religion? I asked myself. The answer of course is more complex. I think that back in the 'olden days' (fill in your own definition) there wasn't really a question of whether or not one was into religion. It was part of the vernacular. So many aspects of life revolved around religion. Disasters and illnesses were ascribed to God, because they didn't know the germ theory of disease or about meterology or plate tectonics.
When I was in Kos a few years ago we went to Hippocrates' hospital at Asklepeion, arguably the birthplace of evidence-based medicine (pity it went into abeyance for so long!). The tour gyide recounted a visit by a group of schoolkids. He asked them if the Greek Gods were real. Yes, replied one small boy. "Because you - and we - make them real in our minds". Very wise small boy.
English culture, although primarily Christian in its roots, also embraces the ancient gods of mythology - Greek, Roman and norse. We read of their feats, or enjoy operas about them without questioning whether they exist. Logically we know they don't, but it's like when we watch Eastenders or read a novel. Of course these characters don't exist in the physical world, but they do in our minds when we experience the performance.
Listening to Sacred Music - let's for argument sake say Handel's Messiah. I don't sit there repeatedly telling myself 'but this isn't true'. I take the view that the Bible is very real, even if not provably true ie this actual story really exists in written form and is widely known, and enjoy the setting of this very well known story without worrying about the metaphysical reality.
In any case, music isn't just about the words. I'm not sure that the music of Messiah would sound as moving if it was set to the words of the telephone directory. On the other hand, I can enjoy Sacred Music in, for example German, which I understand barely at all.
Some people will argue that the music (or the poetry or the fine art) is so good because the artist has Divine Inspiration. In many cases I am sure that they believe they do. Possibly, in other cases, they are happy to fulfil the wishes of the paymaster. But I can't say they have 'Divine Inspiration', because I don't believe in it. My feeling is that people can become very obsessed by an interest, and I don't see religion as being any different. Political activism, football, opera, exams, a particular audit project - I've seen them all take over people's minds. I've experienced it myself. At the very least, one loses perspective and self-awareness, so that every action or observation has a potential link to the subject of the obsession. Granted, a lot of people do it tongue-in-cheek, but there is also research that shows that eg factory productivity is affected by the performance of the local football team. If you want to, you can convince yourself that you are guided by any supernatural Force you might choose. But I'm sure people 'of faith' will disagree with me.
I could also argue that the great music of certain eras tended to be sacred because of the interaction between church and education. In the land of What-Iffery, how many potential geniuses never reached their potential because they never had the opportunity to learn the basics or practice a skill - and this applies just as much to STEM as to Arts? It's unanswerable - and that's before we ask whether talent is innate or trained!
To conclude, I think I like Sacred Music because it's a manifestation of humanism, the talent of human beings to create something that transcends verbal description. I can't explain why music affects me psychologically, and I know that I'm far from alone in that.