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 Gregorian Chant 3-2 "AD MISSAM IN AURORA" - Graduale : Benedictus qui venit in nomine Domini, Gregorian Chant 3-1 "AD MISSAM IN AURORA" - Introitus : Lux fulgebit hodie super nos