In the years I've been making YouTubes, I've never paid royalty for any music. I keep thousands & thousands of mp3s. Most were popular music at one time or another. Many were purchased retail, some have reportedly come from a once free music download service. Amazon music is now my main supplier of retail purchases. Even few obscure "low volume" recordings...like some oom-pah band from Bavaria came from Amazon. Almost all of my YouTubes say "Blocked in some countries". I see that on my end. 99% of the time that country will be but one....my lovely Germany. Very-very occasionally the "blocked in some countries" list will include every nation in the entire universe, including the USA. When that happens, I simply go back & change the music. Use another background song & all will be good. I have a list of sports lead-ins of 10 second clips. Hard to believe those will also violate copyright rules. They were also supplied years ago as "free-ware". Most often, violating copyright rules means absolutely nothing if you don't sell your wares. YouTube will then allow a superimposed ad to appear at the bottom of my video, which can be deleted by the viewer. No big deal. Absolutely none of my videos contain ads, or support ads. Then, I have also gone back & used the same music source that caused trouble 1 yr ago be just fine now.

In other words, I don't worry about copyrighted music. YT folks don't seem to care either.