If the song is over 20 years old, a kid most likely has never heard it and thinks it's yours
The above is House Of 1,000 Pleasures from the band E-Z-O. It's from their debut album, and you probably never heard of it until you heard it here. How did I find out about it? A friend of mine let me borrow an audiocassette of it back when it was new in 1992. And where did he get it from? No idea, I never asked. Probably some other kid my friend knew.
Something a lot of bands do is that if they want to sound original without having to write any music, they simply cover songs that are at least 20 years old...
...but not just any kind of songs.
They'll pick stuff that's slightly or really obscure, so that anyone who hears it thinks it's theirs.
Bands who do this don't claim credit for the song. However, they don't admit the song is a cover either.
Unethical? No, because bands have been doing this for a good long time now.
Back when I used to post cover songs on YouTube before they enacted strict copyright rules (which is why you almost never see covers on YouTube anymore by anyone,) the first time I accidentally ran into this is when I played the riff for Moby Dick by Led Zeppelin. All I did was post the video and titled it "Moby Dick," but made no mention of Zeppelin. Some teen kid posted a comment saying that my riff was awesome; he thought I wrote it. I replied and said it wasn't mine and that it was LZ's, however the point is that the first time that kid EVER heard that song was when I played it.
The more obscure it is, the less likely anyone will recognize it as being written by someone else
If you played Marcy by Norman Greenbaum:
...I guarantee you that nobody will recognize it's not yours. If you play this song with your band when performing, everyone will think you wrote it. Don't say you did, because you didn't, but if nobody asks, don't tell. 🙂
If a cover song you perform proves to be a really popular song you think people would buy, just use SongFile, and then you can sell your cover of the song legally.