: Music is so important in our worship to God. Half of our Liturgy consists of music, but what determines which music is appropriate to use during Mass? The differentiation between sacred and secular music helps determine this. Secular music is music that is not used for religious purposes.
An example of secular music would be Bruce Springsteen's "Born to Run." Sacred music is music that would be used for religious purposes, for instance, "One Bread, One Body." That may bring up the question then as to why some songs are used for a Wedding or Funeral that are secular. The most common one being Pachelbel's "Canon in D." This song is best-known for a bridal procession, which is a part of the Wedding where the Liturgy has not started and therefore seen as appropriate.
It is critical that only sacred music is used during a Liturgy. One reason we celebrate the Liturgy is to give praise and worship to God. This is why we must use songs that are sacred and spiritual. The differentiation between Sacred and Secular can be misunderstood by looking at it as traditional versus contemporary. Sacred music has advanced to incorporate many styles instead of using just the "Hymn" style. We now have pop, country, and many other genres of Sacred music.