Western Christianity sings the Veni Creator whenever it begins something in earnest. It is sung at Vespers of Pentecost, at the consecration of bishops and the ordination of priests, at the opening of councils and synods, at the coronation of kings, where it entered the English coronation rite among others, and, most famously, by the cardinals processing into conclave to elect a pope, so that the hymn has opened every modern papal election. Custom extended the habit to smaller beginnings, the opening of academic years and law terms, and to the first hour of the civil year, sung for the new year in many places.
The logic is the first Pentecost applied, no work of the church undertaken except by invocation of the Spirit who began the church. Music has treated the hymn as monumentally as the liturgy has. The chant melody is one of the most recognizable in the repertoire, Bach and Bruckner among many worked with the text or its German descendant, and Gustav Mahler built the entire first movement of his Eighth Symphony, the Symphony of a Thousand, on Veni Creator Spiritus, setting the ninth century invocation for the largest forces ever assembled for a symphony, a fair measure of the text's standing, a working liturgical hymn that is also one of European culture's permanent possessions.