The USCCB responded to a question on this practice just a few years ago, which answers the question of whether this practice should/can be done. That being said the OP shouldn't have done it without consulting their pastor first.
Dubium: A Major Catholic Basilica in America has the following practice: as the priest processes to the altar, they sing an opening hymn. Then, as the Bishop incenses the altar, they sing the Proper Introit in Gregorian chant. Is this practice licit?
Responsum (Feb 14, 2012 at 7:29 AM): Thank you for your question. Why would you think it illicit to sing both a hymn and the antiphon during the entrance, especially at a more solemn liturgy involving the bishop when the procession and the incensation of the altar might require more music to accompany the action? This is, in fact, the practice in many cathedrals, especially at stational masses of the bishop which include the whole presbyterate of a diocese (such as the Chrism Mass or ordinations).
Executive Director, Secretariat of Divine Worship, USCCB, 3211 4th St. NE, Washington, DC 20017
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