I will focus on an example to try to discuss "spiritual" music versus "genius" music. I don't think there will be much argument if I say that Mozart was a genius. Like a great jazz master, he was known to sit at the piano and riff for long periods, many bars of music. His music set up a musical premise, and he was able to take that premise and view it from all sides, right-side up and upsidedown, and always be able to keep his balance in order to resolve that premise, and it delighted his audiences.
Yet I have heard Mozart live and have been bored. It seems too glib. Too much intellect. When we get to Mozart's later music, however, it begins to change, with the culmination of his Requiem Mass, which I think is deeply spiritual. His later piano concertos also have a depth that is lacking in his earlier music. So, I think I can say that Mozart went through a spiritual transformation as he got closer to death. And I don't think it was strictly Christian. He began to feel the essence of music. Music can delight our minds or move us on a deeper emotional/spiritual level, or with the greatest masters like Bach it can do both.
What do I mean by the essence of music? Why do humans enjoy music? Why did the ancients make music? Instruments have been found over 40,000 years old, and almost certainly older instruments made of wood were destroyed by time. Why would the ancients have taken the time and effort for music when food and shelter were far more important to our survival?
There was something inside the earliest humanity that could only have been expressed through music and other arts, and humanity was obsessed with expressing whatever that was. For so many reasons, especially humanity's early obsession with the sky and stars, I belive that humanity felt connected to the univese. And music was a call to all existence that we too belonged. And that to me is spirituality.
Most music is ego bound. The musician wants to say, "Look at me! I exist!" And by their dazzling intelligence we recognize these masters. But other musicians who are more deeply spiritual I think are saying, "we--all of humanity--belong." We belong to the world in which we live and take sustenance, and we belong to the entire universe.
To me and perhaps you, the feeling of "we belong" is a more potent message than "look at my dazzling intelligence." It can be fun and envigorating to be dazzled by another human intelligence, but it is a much deeper and more satisfying connection to be wise enough to tap into the spiritual message, "We belong."