The Sacred Congregation for Rites issued De musica sacra et sacra liturgia (“Instruction on Sacred Music and Sacred Liturgy”) on 3 September 1958. An excerpt:
Finally, perfect active participation is achieved when there is also sacramental participation, by which “the faithful who are present communicate not only with spiritual affection, but also in reception of the Sacrament of the Eucharist, so that they derive greater fruit from this most blessed Sacrifice.” (Sacred Council of Trent, Session 22, ch. 6; Cf. also Mediator Dei: AAS 39, 565: “It is very fitting and is in fact established by the liturgy, that the people should present themselves at the communion rail after the priest has consumed the sacred species on the altar.”)