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 J. Haydn - Hob III:63 - String Quartet Op. 64 No. 5 in D major, J.C. Bach - W C45 - Sinfonia concertante for oboe, violin, viola & cello in G major, W. A. Mozart - KV 34 - Offertorium in Festo Sancti Benedicti in C major