St. Gregory the Great reported the same route was followed and a Mass held at St. Peter’s. Purpose is to ask God’s blessing for a good harvest. If there is a procession, a Votive Mass of the Rogations, without Gloria or Credo, Preface of Easter, commemoration of St. Mark, is celebrated.
Litany of the Saints is said or sung during the procession, this can be in the vernacular. If no procession, Mass of St. Mark, Disciple of St. Peter, who called him his son. His Gospel reflects voice of St. Peter. Martyred in Alexandria, St. Mark’s body was later taken to the Cathedral in Venice in the IX Century where it is on display for the veneration of the faithful.
For those obligated to say the breviary, the Litany of the Saints, with its prayers must be recited and in Latin.