Worship services of the Churches of Christ are marked by the complete absence of musical instruments. All of the music is unaccompanied singing. The music heard most frequently is, nevertheless, quite diverse and includes a wide range of classic hymns and gospel songs. While congregational singing is the foundation of worship music, choirs and special singing groups are sometimes included. Many congregations now use modern songs that speak more directly to younger people in place of older texts, with their agricultural and seafaring metaphors. The visual arts are not emphasized, although increased attention is being given to the worship setting. Drama is slowly being introduced in some churches.