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 F. Mendelssohn - Ottetto per archi in Mi bemolle maggiore op. 20, LUDWIG VAN BEETHOVEN - Serenade for string trio op. 8 (four movements)