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 Dudenbostel Mandola played by Mike Whtehead, Bales Banjos, I've Found a New Baby - The Mandolin Symposium 2012 - Jesse Cobb and Solly Burton