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 Pacifica Quartet - Mendelsohn Quartet in E minor, Op. 44 No. 2; II. Scherzo: Allegro di molto, Ariel Quartet - Haydn: Quartet in E-flat major, Op. 33 No. 2, "Joke", Pacifica Quartet - Mendelssohn Quartet in A minor, Op. 13; IV. Presto