In the Maundy Thursday Rite in the old Roman Pontifical, the climax of the rite was the Consecration of the Chrism: the oil used to confer the Spirit in Consignation and Ordination; the oil which some Patristic texts see as so Spirit-filled as to be comparable with the Blessed Sacrament. This was performed by the Pontiff; but the Pontiff was not alone. If you have read the previous posts on concelebration, you know what I'm going to say: Yup! the bishop was accompanied by a representative Twelve Priests (a significant number?) dressed in chasubles. At the end of the rite, the Bishop breathed on the Oil of Chrism. Spiritus, Pneuma, is breath; the Holy Spirit is the Breath of God; the Bishop is the Spirit-filled Minister of his Church, the pneumatic organ of the continuance of its sacramental life, in and through the Spirit, through space and time. So, like Jesus breathing forth the Spirit upon the Cross, the Bishop breathes the Spirit upon the Oil. And so does somebody else. Yes: again you've got it: so do those twelve parati (chasuble-clad) sacerdotes. With their bishop (they could not do it without him) they halant, breath, the Spirit upon the Chrism. They are one with him; his presbyterium; his corporate collegial body of ministers who apart from him can do nothing but with him share his Spiritual, Sacramental, fecundity.
We have been left, in the newer rites, a pale shadow of this collegiality of action, this concelebration, in the rubric requiring the priests present to join with the Bishop in extending their hands during the Prayer for the Consecration of the Chrism.