For a long time, the Service of the Word was the only part of the Divine Service open to visitors and those in the process of joining the Church. The Service of the Word is also called the Service of Catechumens, meaning Service of Learners.
In the early church, visitors were only permitted in the Service of the Word. The Service of the Sacrament was reserved for baptized Christians only. When the Service of the Word ended, visitors and catechumens would be dismissed. Catechumens means learners. It was used as the term to describe people wanting to join the Church.
The Service of the Word begins with the Introit and ends with the Prayer of the Church. Introit means “He enters”. It is a Psalm.
The practice of singing/chanting Psalms is an ancient practice of the faithful. It was done by believers in the Old Testament, New Testament, and throughout church history. Each Sunday, when we chant the Introit, we are carrying on a practice that Jesus did. To think, whatever psalm you’re singing, has been sung by Christ and the saints for the past 3,000 years.