The celebrants of the sacramental liturgy
For the purpose of assisting the work of the common priesthood of the faithful, other particular ministries also exist, not consecrated by the sacrament of Holy Orders; their functions are determined by the bishops, in accord with liturgical traditions and pastoral needs. "Servers, readers, commentators, and members of the choir also exercise a genuine liturgical function."
Source: Catechism of the Catholic Church (Vatican.va)