Spotify was built from pirated music, so a legal grey area?
Youtube has a questionable past, especially as far as piracy goes.
Also, most Generative AI tools have very questionable origins, and seem to go legit all the time.
I don't know if IMSLP is considered legal atm :P but everyone uses it!

I've seen people sell scores on Bandcamp...

I usually mostly want to know what the internet experience is like for people in other regions and other languages. I can see differences between my Dutch language internet and the 'world wide web', the internet must exist out of all kinds of local internets.