The role music plays in one's spiritual life is simply not quantifiable. Suffice to say that for many people, music is the way they express their religious feelings. Most everyone has their favorite hymns, the ones they know by heart. My mother and her three sisters used to sing in churches when they were teens back in the 1940's and they knew so many hymns by heart. When I get together with my aunts and my cousins on my mother's side, somebody always wants to have a hymn sing, and I am amazed at how many hymns my aunts and cousins and I know.
In my own journey, music has been part and parcel of my walk with/toward/seeking God. As a junior high student, I played the piano for Vacation Bible School at my Southern Baptist church for several years . . . Stand Up, Stand Up for Jesus; All Hail the Power of Jesus' Name; O, How I Love Jesus; among others, were the standards. When I became an Episcopalian, it was the music that drew me first - Lo! He Comes, With Clouds Descending and singing the O Antiphons during Advent, Easter morning with brass and timpani, chanting the Psalms and the Eucharistic Prayer and singing the service music. The King of Love My Shepherd Is, At the Name of Jesus, What Wondrous Love is This? The Pange lingua on Maundy Thursday. I love how the hymns are identified by their tune names. I have a long list of favorites, but I'll spare you.
We are formed by singing and listening to music, just as we are formed by reading scripture or hearing it read. Some hymns express a theology (such as the Pange lingua (Sing my Tongue the Mystery Telling), which was written by Thomas Aquinas and lays out his Eucharistic theology), tell a story (The First Nowell), paraphrase scripture (My Shepherd Will Supply My Need), or otherwise express Christian duty (Lift Every Voice and Sing), praise (When Morning Gilds the Skies), themes from a liturgical season (Songs of Thankfulness and Praise) or doctrine (Ah, Holy Jesus).
On Ash Wednesday I heard Marcel Dupre's Lamento. The first time I heard it was on a Good Friday. My husband told me that he wants that played at his funeral (which should not be any time soon, I hasten to add).
Music helps us with our religious feelings and expression. Sometimes we sing by heart, sometimes we listen to someone else play or sing, sometimes we sing together, sometimes alone, sometimes we suddenly "get" something as we read the words as we sing, but always with music we are engaged in worship, in drawing nearer to God. As St. Augustine of Hippo said (and I both paraphrase and abridge here), "One who sings, prays twice."