The esteemed and informative Rubricarius of the St. Lawrence Press has published a detailed post on the ancient Vigil of Pentecost, suppressed in 1956—probably, as he notes, because it would remind too many people of the old Holy Saturday Mass.
|Violet penitential vestments, the "folded chasubles," worn by the deacon
and subdeacon during a Lenten Mass at the Pantheon
The old Vigil would start, as all Vigils did, after None, which is interesting as it bridges the times between the office of the day and first Vespers of the feast. A true practice of anticipation! The Mass itself begins with violet penitential vestments and six prophecies, all borrowed from Pascha's Vigil, are read with unique collects at the end. The collects and other prayers of this Mass have an even more baptismal undertone than those of the Paschal Vigil!—and should, as on Pentecost the Church baptized 3,000 people. The baptismal font if blessed, people are sparged (without that "Renewal of Baptismal Promises"), and converts are baptized. The Litanies of Saints again acts as an introit and Mass ensues. No candles are carried at the Gospel, a symbol that the feast is only expected, but has not yet arrived. First Vespers are sung later.
As Rubricarius points out at the end of his post, the Johannine Missal misses all of this and it is treated as a glorified ferial day. The rites of Paul VI actually improve on this dire situation by restoring the readings.
Depending on your location, you may have prayed first Vespers by now. If so, happy Pentecost!