Michael Pastucha wrote: ... "written by Will S. Hays. In 1870 ... public domain. ... later copyright holders of songs that are essentially very similar... my video may have ads placed on it to maybe "pay" the real and unnamed copyright holder(s)."
Michael, I would recommend that you dispute the claim. Don't let fraudulent music-industry scammers make money off of YOUR playing! Do it on principle even though it may take a minute or two to click through the various things required to contest the copyright claim.
I've only had reason to do this twice, several years back. Once was because of some copyright-troll's fraudulent claim on me playing my own arrangement of a 200-year-old public domain instrumental piece. Fortunately, disputing claims was quick and easy. In each instance, about a month later, YouTube emailed me that they'd dropped the copyright claim.
A new thing I've noticed the last several years with copyright claims, though, is that YouTube no longer emails you copyright claim notices - instead they just let someone claim copyright of your video without notifying you. You have to occasionally manually check the appropriate area in your YouTube account's info panel to see the current copyright status of each of your videos, to see if any of them have changed copyright status.
Martin wrote: "Adverts on Youtube videos"
About their new policy of ads on everything regardless of copyright, yeah that sucks. I hate thinking that my viewers might think I authorized any such ads, because I haven't and never will.
The computers I maintain here at the house all run adblockers, as has been the case for a very long time. So we don't have to see ads on other people's stuff. But probably many people don't even know about adblockers. And some websites are becoming increasingly cagey about detecting and blocking the adblockers, it's like a cat-and-mouse game to see who can prevail, the advertisers or the rest of us. (I have always blocked ads for security reasons, because so many of them over the years have been infested with various forms of malware that can harm one's computer.)
Too bad YouTube is essentially a monopoly. What else is there, Vimeo? I haven't tried Vimeo, is it just as bad but in different ways? Even years ago when I used to have my own website and domain name, I wouldn't have been able to post videos on my own website because it was a budget site with low bandwidth caps (too many video views would have resulted in me paying the webhost $$ over-usage fees, thus I would have been losing more money with each additional view - clearly not a monetizing strategy! Lol) as videos gobble up lots and lots of bandwidth. At least YouTube doesn't charge for bandwidth, so maybe it's not all bad...
Martin wrote: ... "they specifically exclude any controversial content on the grounds that it may be "brand damaging" to advertisers. So maybe we should start every video with some choice swear words or a flat earther rant..."
Lol! You might be onto something there. Except then your videos might be adorned with flat-earther ads ("Build Your Own Rocket! Amaze Your Friends, Prove Earth Is Flat!") and ads for "Learn The Best Swear Words In 10 Languages!" There's a market for everything, it seems.