Here is the news story about how the Catholic Church in Kerala, India, in addition to publishing a list of approved music, has banned non-Catholics from singing at Mass. I know nothing about the state of Catholic music in India but I'm guessing that it suffers from many of the same problems we have in the U.S.. The decision to ban non-Catholics might be a reaction to the fact, as mention in this article, that some of the most popular music was actually written by Hindus (who make up 56% of the population). No doubt that those behind this decision, however misdirected, believe that they are taking a step toward re-Catholicizing music at Mass.
Of course such a course of action in the US would be devastating to choirs all over the country. The musical talent pool within the Catholic Church has been drained over the last 40 years, to the point that many parishes have only a few people who can read music at all, much less sing it. And this should be no surprise when you consider the dumbed-down hymn books and childish styles that are pervasive at liturgy. This music has not been compatible with the Council's wish that choirs be more heavily cultivated than in the past. This means that means most scholas must rely, in part, on non-Catholics to sing genuine Catholic music in the places where it has made a come back. This will be true for decades to come, I'm quite certain.