This was shared on FB. In one of the groups, someone with knowledge of Swedish took the time to translate Fr. Anders' introduction to the Mass in the video. A transcript of the translation follows:
"Five hundred years ago, the universe seemed much more understandable than it does for us. All of existence was framed by a number of ceremonies and behavioral patterns which were a matter of course for people at the time. And the most important of them was the Holy Mass - that ring of charged words and actions which surround the central mystery in the Christian faith: That Jesus becomes man anew in the creatures of bread and wine.
"We have reconstructed a High Mass from 500 years ago in an ordinary Swedish parish church, namely in Endre Church, one mile east of Visby in Gotland. We imagined ourselves to be participating in this high mass on an autumn Sunday in the middle of the 15th century. It is local people who are participating in clothes typical for the time, and we have tried as much as possible to reconstruct [something to do with (worship) services] in the Diocese of Linköping at that time - since Gotland belonged to that diocese. "
The service is conducted in an incomprehensible language, a language incomprehensible to the people: Latin. Because church services at the time were not considered a medium for communicating information, except for silent prayers. Just as one cannot describe what is fascinating about a melody or a sight, one shouldn't be able to understand or describe the central mystery of the universe. The congregation waits for the central moment, when the bread and wine shall be transformed into the body and blood of Christ.
"The priest was helped by a chorister, perhaps the [experienced?] youth whom [his soul has discovered?] and who with time would be sent to Linköping in order to attend the cathedral school. Songs, mostly from the Bible, were sung by the local cantor. We don't know exactly how the music went in the medieval churches. Maybe Endre Church had a specific order which required a qualified cantor like the one we shall see here.
"The Sunday service began when the priest sprinkled Holy Water on the congregation. This was to remind them that they had become members of the Christian church through baptism. The Holy Water would drive away all the powers of evil. "Let us now place ourselves in the Middle Ages. Let us try to grasp the atmosphere in a normal Swedish parish church, in a time where man still believed himself cast out into an empty, cold existence, when Europe was still unified, and when the central mystery around which everything revolved was that Jesus Christ, had become man, had died, and risen again for all."