In Hoc Signo 312:
The Roman Rite of the Eucharist (Mass/Divine Liturgy) and the Byzantine Rite vary greatly in the details, but they share a common core. As a seminary student I did an independent student specifically on the Roman Rite. I have attended and view videos of the Tridentine (Extradordinary form) Latin Mass and of the Novus Ordo Missae that is used in most Roman Catholic parishes in our day. In some ways the Latin Mass is more like the Byzantine Liturgy with the regular use of incense, the use of chant and fixed hymns, the sense of reverence expressed by little details like servers kissing the hand of the priest when handing him something or taking something from him (like palm branches on Palm Sunday), and the orientation of the priest facing east like the people do. In other ways, the Novus Ordo is more similar, like the use of a full responsorial psalm, which, when sung, is very similar to the prokeimenon in the Byzantine Liturgy, sung just before the Epistle reading. Although Orthodox priests always face East, the altar is actually free standing like it is in modern Catholic churches.
At the core, the Roman Rite and the Byzantine Rite share in common a basic order of hymns and prayers, epistle, gospel, creed, offertory, eucharistic prayer, and participation in Holy Communion. In the Byzantine Rite, the Creed comes after the offertory, which is called the Great Entrance and is done more elaborately than in the Roman Rite. The Byzantine Rite, whether served in a great cathedral or in a small village church in Greece, Russia, or America, is a scaled-down version of the Liturgy served in Constantinople in the 900s, with relatively few changes. I say relatively because there certainly are some. Even today, though, liturgical practice in the Orthodox Church even today is informed by the rubrics we have from the 10th century.
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