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 Quatuor Ysaye - Schumann SQ Op.41 No.3 (1/4), Quatuor Ysaye - Beethoven SQ Op.59 No.2 (2/4)