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 Mystery, original work for cello quartet by Paul Fleury, Dohnanyi Serenade for Violin, Viola and Cello in CMaj Op. 10, Strummed Pizzicato on Cello (Tutorial)