I make videos occasionally and upload them to YouTube. 

If I want to add music to a clip. I go to the "freemusicarchive.org" site and search for music available with a Creative Commons Attribution Only ("CC-BY") license. 

This means the track can be used in any context - including for commercial use - provided you attribute the music and provide a link to it. 

On YouTube, I do this both in the description and in the video in the credits.

What I have been finding is that occasionally some artist or other will remove the music from CC-BY and I then find myself with a copyright claim against my video.....a year or more after I uploaded it, at which time it was perfectly legitimate.

I'll have to read up on Creative Commons licensing. Fair enough requiring all FUTURE works to abide by a different license, but it seems a bit off to make a work available on an attribution only basis....and then if people actually USE it, you then withdraw it and ping them for copyright. That just feels like a scam or some kind of fraud.