The early Christian church is credited with developing plainsong, also known as plainchant. This form of church music was popular through the Middle Ages, relying on chanted or sung words and not featuring any musical instruments.
The earliest examples of plainsong emerged around A.D.100 soon after the establishment of the first churches. According to Christian tradition, this was the only sort of music permitted for use in worship services at that time. The philosophical basis for this was the idea that the purpose of music was to increase a listener's openness to spiritual reflections and ideas. This is the reason why the music was left without accompaniment and only featured a melody.
In the earliest types of plainsong, no musical notation was used. Over time, practitioners developed a symbol known as "neumes" to show the desired pitch and phrasing of syllables. Around A.D. 600, Pope Gregory I, also called Gregory the Great, decided to gather all of the different sorts of plainsong into one collection. This amalgamation was eventually known in the church as the Gregorian Chant. Today, soloists and choirs in Roman Catholic churches still perform Gregorian Chants, set to a Latin text and then sung without any instrumental accompaniment.