[ninenot]

The Introit sets the theme of the Mass. As you know, the Introit is "the entrance antiphon" and only if the Introit is NOT sung is there an "entrance hymn."

Of course, it was present in Rome in the early liturgies--THAT is provable, not speculative. But because a trained schola is necessary to sing it, and it remained in Latin, it was quietly dropped by neo-conservatives and Libbies alike.

[traditionalist]

When I was in the choir at the Church of Notre Dame near Columbia University in New York, the men in the Choir used to chant the Introit in Latin at Novus Ordo masses. Unfortunately, this is an extremely rare practice.