Following up on Adam Wood's intriguing idea that "participation" might have been understood by the Council Fathers in a more metaphysical sense than we might understand it today, I thought these paragraphs from Mediator Dei
might make for some interesting background reading.
102. All the elements of the liturgy, then, would have us reproduce in our hearts the likeness of the divine Redeemer through the mystery of the cross, according to the words of the Apostle of the Gentiles, "With Christ I am nailed to the cross. I live, now not I, but Christ liveth in me." Thus we become a victim, as it were, along with Christ to increase the glory of the eternal Father.
103. Let this, then, be the intention and aspiration of the faithful, when they offer up the divine Victim in the Mass. For if, as St. Augustine writes, our mystery is enacted on the Lord's table, that is Christ our Lord Himself, who is the Head and symbol of that union through which we are the body of Christ and members of His Body; if St. Robert Bellarmine teaches, according to the mind of the Doctor of Hippo, that in the sacrifice of the altar there is signified the general sacrifice by which the whole Mystical Body of Christ, that is, all the city of redeemed, is offered up to God through Christ, the High Priest: nothing can be conceived more just or fitting than that all of us in union with our Head, who suffered for our sake, should also sacrifice ourselves to the eternal Father. For in the sacrament of the altar, as the same St. Augustine has it, the Church is made to see that in what she offers she herself is offered.
104. Let the faithful, therefore, consider to what a high dignity they are raised by the sacrament of baptism. They should not think it enough to participate in the eucharistic sacrifice with that general intention which befits members of Christ and children of the Church, but let them further, in keeping with the spirit of the sacred liturgy, be most closely united with the High Priest and His earthly minister, at the time the consecration of the divine Victim is enacted, and at that time especially when those solemn words are pronounced, "By Him and with Him and in Him is to Thee, God the Father almighty, in the unity of the Holy Ghost, all honor and glory for ever and ever"; to these words in fact the people answer, "Amen." Nor should Christians forget to offer themselves, their cares, their sorrows, their distress and their necessities in union with their divine Savior upon the cross.
105. Therefore, they are to be praised who, with the idea of getting the Christian people to take part more easily and more fruitfully in the Mass, strive to make them familiar with the "Roman Missal," so that the faithful, united with the priest, may pray together in the very words and sentiments of the Church. They also are to be commended who strive to make the liturgy even in an external way a sacred act in which all who are present may share. This can be done in more than one way, when, for instance, the whole congregation, in accordance with the rules of the liturgy, either answer the priest in an orderly and fitting manner, or sing hymns suitable to the different parts of the Mass, or do both, or finally in high Masses when they answer the prayers of the minister of Jesus Christ and also sing the liturgical chant.
100. These methods of participation in the Mass are to be approved and recommended when they are in complete agreement with the precepts of the Church and the rubrics of the liturgy. Their chief aim is to foster and promote the people's piety and intimate union with Christ and His visible minister and to arouse those internal sentiments and dispositions which should make our hearts become like to that of the High Priest of the New Testament. However, though they show also in an outward manner that the very nature of the sacrifice, as offered by the Mediator between God and men, must be regarded as the act of the whole Mystical Body of Christ, still they are by no means necessary to constitute it a public act or to give it a social character. And besides, a "dialogue" Mass of this kind cannot replace the high Mass, which, as a matter of fact, though it should be offered with only the sacred ministers present, possesses its own special dignity due to the impressive character of its ritual and the magnificence of its ceremonies. The splendor and grandeur of a high Mass, however, are very much increased if, as the Church desires, the people are present in great numbers and with devotion.
107. It is to be observed, also, that they have strayed from the path of truth and right reason who, led away by false opinions, make so much of these accidentals as to presume to assert that without them the Mass cannot fulfill its appointed end.
108. Many of the faithful are unable to use the Roman missal even though it is written in the vernacular; nor are all capable of understanding correctly the liturgical rites and formulas. So varied and diverse are men's talents and characters that it is impossible for all to be moved and attracted to the same extent by community prayers, hymns and liturgical services. Moreover, the needs and inclinations of all are not the same, nor are they always constant in the same individual. Who, then, would say, on account of such a prejudice, that all these Christians cannot participate in the Mass nor share its fruits? On the contrary, they can adopt some other method which proves easier for certain people; for instance, they can lovingly meditate on the mysteries of Jesus Christ or perform other exercises of piety or recite prayers which, though they differ from the sacred rites, are still essentially in harmony with them.
95. Gal. 2:19-20.
96. Cf. Serm. 272.
97. Cf. 1 Cor. 12:27.
98. Cf. Eph. 5:30.
99. Cf. Saint Robert Bellarmine, De Missa, 2, c. 8.
100. Cf. De Civitate Dei, Book 10, c. 6.
101. Roman Missal, Canon of the Mass.
102. Cf. 1 Tim. 2:5.