Since before recorded history, music has been used to express humankind's most profound ideas and emotions. It should come as no surprise that music has become an integral part of virtually every major religious belief system, since both theology and music seek to explore aspects of life that transcend mundane experience. Music is nearly always part of the worship structure of both liturgical and non-liturgical traditions, often as canonical texts set to music or in other, more flexible formats that give insight into popular theology. Theology and music also interact outside of religious structures, as seen in the often turbulent relationship between religion and secular music.
A very common form of religious worship consists of singing scriptures set to music. This can be seen in the Jewish prayer services known as nusach, in the singing of Sutras in some Buddhist traditions, or in any of a number of Psalms sung in Christian worship services. One purpose of this is educational, since worshipers are more likely to remember something if they have sung it. Beyond that, however, setting a text to music may also deepen its theological meaning. The same text set to a different style of music may convey a very different emotion or concept.
Among Christian traditions, Catholicism has the most structured theology of music, with a number of church documents codifying the purpose of music in worship. In Catholic theology, music is not simply an embellishment of the liturgy, but an integral part of what is known as the "liturgical mystery." Not only the text, but also the music is pre-determined according to the church calendar. According to this view, liturgy combines text with action, allowing the worshiper to participate meaningfully in the service by re-enacting the life, death and resurrection of Christ. One way this is done is through congregational singing.
A less structured connection exists between theology and music in non-liturgical traditions. Folk music often carries religious themes that give voice to the concerns and theology of a particular group. African American spirituals, for instance, often speak powerfully about freedom from oppression. Popular religious songs often leave room for improvisation, which its proponents may view as key to sincere emotion. Critics of this style of music often claim that it sacrifices aesthetic and theological rigor for the sake of spontaneity, but others see its accessibility as working in its favor.
Even music that does not have overtly religious meaning may interact with theology. Religiously conservatives sometimes claim that some secular music is antithetical to the goals of their faith and that the faithful ought to reject music that is not a part of their religious tradition. On the other hand, some people believe that there is a connection between divine creative power and humans' creative power, which sanctifies even secular music. This belief implies a connection between theology and music that goes beyond the intended purpose of a particular piece of music, to comment on the nature of music itself. Most people, however, fall somewhere in between these two extremes.