This came about when I was thinking. Before I give my views on the matter, let me define a few things:
Spirituality: The way in which any person connects to any sort of higher state (or to a higher power, if that's your belief).
Faith: The connection you have with the higher state that most usually dictates your mores and ways of being.
Religion: How a person connects with others over similar faiths or spirituality.
Spirituality fuels faith and religion and the "connection," faith dictates the way you go about religion and spirituality, and religion is how you interact based on your spirituality and faith. All interrelated.
Given those, let me say this: music is a form of spirituality. Put on a record, a damn good one, and it takes you somewhere else. You connect with something else. A higher power, something more than yourself. You feel...different. Everything sort of clicks when that record starts playing. All sorts of problems melt away and it's just you, the music, and that strange plane you find yourself on. This is what every good record does. It takes you somewhere else, it connects you with something bigger than yourself. A record doesn't have to deal with anything supernatural to connect you in this spiritual manner. Sigur Rós is a good example. Who knows what they're saying? It doesn't matter. Because it's stark and beautiful and when you put it on, you connect to something else. You put on the Beatles (i.e. Sgt. Pepper's Lonely Hearts Club Band) and you are literally transported to somewhere else. And because of how the Beatles were so damn good, the music itself connected you to a higher power. It doesn't matter that they weren't preaching anything. You don't have to preach it to be spiritual. Connecting to that higher plane or being is just as easy (if perhaps more easier) without all that preaching.
Music doesn't have a lot to do with faith, unless you're talking about those who tend to preach the art. Then you're getting dicey. Bob Dylan and John Lennon are pretty good examples of "faith" artists. Their faith fuels their music and vice versa. When done right it's extremely powerful, but when not done right it's downright pitiful. I don't care if you don't agree with John Lennon on the whole, but when he starts singing "God is a concept by which we measure our pain," don't you fucking believe him for a second? And that you're like "Well, shit, maybe..." before you reconcile your views with his and continue on your merry way. It's kinda like that.
Religion is a strange beast, because anything could be religious. Going to a concert, let's say Pavement (my current dig. Also...REUNITED! At least for a bit). You connect with others over the same thing (Pavement's music or whatnot) and by listening to their show you connect with that higher plane/power. That's just as religious as going to church, connecting with others over communion or the gospel and then connecting to basically Jesus or God, depending on the extension.
Let me get back to a previous point, "you don't have to preach it to be spiritual." This is why Christian rock sucks. I'm going to be honest. It is terrible, it's un-listenable. Even as a non-religious guy (but note that this is separate from faith and spirituality) I would be more inclined on exploring the more Christian aspects of existence if it weren't for the fucking terrible music. Call it really slight, really conceited of me, but pardon me for thinking that music has limitless potential in influencing people, and for that potential to be misused or not used at all kills me. It in no way facilitates any connection to any higher power. Part of this is its extreme gaudiness in whatever lavish praise it hopes to lay on. This is the analogy I would use:
Remember Indiana Jones & the Last Crusade? The almost final scene where they finally find the Holy Grail? All the greedy ones thought that the Holy Grail was the most lavishly ornamented, gilded cup, but guess what? They sucked it up and died...because they were dumb. But look at ol' Indy. He picks the least convincing cup. The most humble cup. And hiyo! Success.
Christian rock, in some extension (and probably exaggeration) is like that lavishly ornamented, gilded cup. It's unfit to be a proper vessel for spirituality. Laying on the praise in the way Christian rock does seems to me to be extravangant, unnecessary, and altogether detrimental to that spiritual process. It's un-intuitive, un-imaginative, and everything. If you concede (as I do) that there is a higher power out there, you have to think that he/she/it'd be pretty pissed and/or disappointed if they figured out what sort of janky vessel their "holy water" was being offered in. And if you believe that said being made us, they'd probably be still more pissed that all our creative energies (given that we are likely the only species that has developed this unique power of art) were terribly going to waste. And, if it's your kind of book, you figure that as the humble carpenter does his work, he is rewarded accordingly. Not in any way like it is now.
If you want to explore religion and faith in song, there are better ways of doing it. Tell a story with some meaning, put your characters in between a rock and a hard place and see where their faith takes them. That's more interesting and worthwhile. Challenge them and test their faith because if they aren't challenged, where do they go? Nowhere at all. Your characters do nothing, and by extension you aren't doing anything either as the listener or the creator. What use is that, really? You're not connecting yourself to that higher plane or that higher being. Then what are you even doing listening to music? You shouldn't be if that's your goal.
Alright, I'm getting off the soapbox now...