A friend snagged this old document on eBay: The White List of the Society of St. Gregory, published in 1947 with its 1954 supplement. If you are interested in the history of Catholic music in the United States, this document will keep you tied up for several evenings of gawking at the decisions made by some of the best Church musicians of that time.
It includes a blanket endorsement of most 16th century music but seems to leave the English Catholic composers out. On the specifics, vast amounts of suitable music is completely absent, such that Palestrina and Victoria have only a few Masses mentioned (Josquin: 0) whereas Singenberger, Perosi, and the Ceacilians are everywhere. I don't know enough about music history to say but it seems that most of the music named herein didn't stand anyone's test of time.
Mozart, by the way, is on both the white and black list.
Also uploaded is a fine compilation of Papal texts concerning music. This obviously holds up.
Also, if you are curious about the black list, this is extracted for your reading pleasure.
As you read, you will note the ubiquitious presence of approved publishers and editors, and one can't be wonder about fiduciary issues that might have been at work here.
It makes sense to view these documents in light of new talk about a new approved music list from the US Bishops. This is a path fraught with danger, or so it seems to me. Some people believe that the White List ended up causing more harm than good. I can only imagine that some people might believe a new white list is the last best hope for salvaging music of the 1970s that seems to be on its way to the dustbin of history. If so, a white list is not likely to do much to save it.