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 "Olana" by Kyle Gann, "Prelude I" by Christopher Deane, "The Whimsical Nature of Small Particle Physics" by Ben Wahlund (PASIC 2010)