videos in AudioSet
A list of about a million ten-second YouTube clips, each labelled with the sounds in it, that Google published in 2017. Labs use it to train and test general audio and music models.
Including Old Roman Catholic Chant - Invocabit me et ego exaudiam eum, Old Roman Catholic Chant - Resurrexi et adhuc tecum sum, Glagolitic chant - Prosti moj Bože