Seems Jeff answered the question pretty well.

Publishers / Copyright Holders have the right to have content blocked on YouTube. I've posted some stuff on my own channel that had some bits of copyrighted music here or there, and I pretty quickly get a notice. Sometimes it gets blocked / taken down, and sometimes the publishers are fine with it. Hard to predict, because it's up to them.

By the way, there are companies who specialize in sniffing out where copyright music is used without permission on YouTube and alerting the owners. I also recently had some music playing in the background when I was live streaming on YouTube and it canceled my stream. So the algorithms are getting pretty good these days!

-Carl.