I have to open with a disclaimer: I'm not at all sorry for that pun.
The world had music long before it had humankind. Humpback whales sing to each other - though we don't know why - and birds harmonize in the trees. Nature makes its own sounds, and if the hundreds of "ambience" playlists on youtube don't convince you that its making music, then you need to spend more time amongst the bees and the trees. We'll never know why the first human started to sing or what inspired them or what they sang about, but the earliest examples of notated music comes from a 4,000 year old Sumerian tablet; a hymn honouring Lipit-Ishtar. It stands to reason that singing as a form of worshipping the gods probably swiftly followed.
In the twenty first century, music is impossible to ignore. We hear it on the car radio. We can stream it on a hundred different services. We have cds, and records, and casettes and iTunes. We sing when we're happy, we sing to our children. To quote August Rush:
"The music is all around us, all you have to do... is listen."
But what does music have to do with spiritwork - or indeed, religion in general? As it turns out, rather a lot. There are hymns, of course, as I've mentioned before, defined by Merriam-Webster as "a metrical composition adapted for singing in a religious service". Traditional hymns (in Christianity, at least) are what you're probably thinking of if you imagine walking into a cathedral, largely medieval pieces with lyrics from psalms and the Bible. Other religions have their own conventions behind hymns, and their own source materials and anthologies, and sometimes a hymn is just making music, creating for your gods. There are also modern hymns, written by modern practitioners.
Something I create in my practice, however, is devotional playlists. While these do sometimes have songs that were written for or about my deities on them, they are mostly just pieces of music that make me think about them. Odin's playlist, for example, has music ranging from Alchemical Poetry's rendition of 'Song for Odin', to the dulcet tones of the spectacularly Odinic Hozier, all the way to Big & Rich's 'Save a Horse, Ride a Cowboy'. Why do I put these playlists together? Partly because I've been making mix-taps because I was ten, and partly as a devotional act.
Compiling a playlist is a very personal thing. You put your energy into choosing the songs, and creating the list. Depending on how you godphone or communicate with your deities, you can spend time with them while putting the music together. However you go about it, it forces you to think of personal correspondences; "what about this song reminds me of Hermes?" or "why do I think of Loki whenever I hear this song on the radio?" Sometimes it can be inspired by the mythology and research of the religion, and other times, it does something special and points you towards areas of your spiritwork that you need to focus on.
For example, I have a song - which I put on my Odin playlist because it lists his names - that I never skip whenever it plays in my full library (which is about 90 hours long, last I checked). Odin has used this song to tell me he wants to talk to me often enough that it elicits a Pavlovian response, at this point. Another time, Thor centered me by shuffling my playlist to 'Cirice' by Ghost, and so now I play that song when I'm struggling with anxiety or want to relax with him as it helps me make a physical connection as well as an aural one.
And so as you see, music plays another role in spiritwork; catching your attention. Many polytheists use shufflemancy as a form of divination (hitting shuffle on their music library, and analysing the lyrics). Others - including myself - have experiences where deities send them music, like I've said above. And it doesn't have to be the spirit who does the 'heavy lifting', as it were. Music with heavy drums (as an example) can be useful as an aid to put you in a trance-like state, which can reduce the static feedback that makes meditating to talk to your deities more difficult.
Playing music yourself - your playlist, drums, or an instrument - can also be both a beacon and a devotional act. It can be used in rituals, as a way to pass on stories of your spirits to new generations and more. Even song in the form of dancing has its place in spiritwork - both traditionally, or dancing around like nobody is watching as a way to 'hang out' with Loki. And one final area that I would like to touch on very, very briefly (it's not something I know a lot about) is musical healing. Researchers have used musical therapy as a way to treat symptoms such as arthritis, as well as to help the peace of mind of those with degenerative memory conditions. It's also been used similarly in the healing of chakras in Hinduism.
So next time you're listening to music, think about your spiritwork. Think about what you need to work on, or relationships that you'd like to strengthen. Ask your spirits if they'd like you to incorporate it into your faith. Put on some music to turn your mind off, and see what happens. And if you've read this whole article and gone "well, duh" then here's a little homework for you: do some research into the Music of the Spheres. Because after all, how else can I live up to my reputation than by forcing you to relive the opening pun again...