I've been wondering if I can do SoundSlice.com transcriptions on Django youtube videos.
My understanding is that I cannot, because the songs are still copyrighted. As of 2019 it looks like one can assume that most music published after 1924 is still under copyright in the US.
Here are some internet resources for music copyright:
Comments
You wouldn't be the first person to do it.
https://www.soundslice.com/slices/1f1cc/