Conducting the medieval mass was different from today’s mass. For one thing, it was sung in Latin. There was no concept that most worshippers should understand the content.
Even many of the priests, if they were humble country clerics, did not understand the words they said. They learned them by rote and gabbled them rapidly. This was one of the abuses that led Luther to demand a Bible in the vernacular.
Often in monasteries masses were sung rather than spoken. The previous version of this article linked to a magnificent sung medieval mass by Jacob Obrecht, but unfortunately it is no longer available.
The Franco-Flemish Jacob Obrecht (c 1457/8 – to c July/August 1505) was the most famous composer of masses, motets and songs in Europe of the late 15th century. The wikipedia article links to many of his hundreds of still existing sacred and secular works, many of which exist as recordings. He was only eclipsed after his death by Josquin des Prez.
Listening to a choir conducting a medieval mass is a sublime experience. Do so, if you have the opportunity, whatever your religious persuasion.