Regarding difficulty - on lower difficulties it’ll take longer to earn up the medals (though the major order rewards definitely help there) but I actually think it’s faster to farm super credits on the easiest 3 difficulties.

Moises is an app that isn’t directly intended for making karaoke versions of songs, but you could use it for that purpose. It separates songs out into their parts (guitar, keys, vocals, drum, etc) using assistive AI. You get a few free songs but you have to pay a subscription for more than that.

There’s also StarMaker but you’re limited to the catalog they have and it’s definitely got some dark pattern design. Can be a bit fun but I deleted it pretty quickly.

did not actually file copyrights on their art with the U.S. Copyright Office.

The way they’ve worded this isn’t really a sufficient explanation of how this works. An artist is automatically granted copyright upon the creation of a work, so it’s not that they don’t have the right to protect their work. It’s just that, without registration, you cannot file a lawsuit to protect your work.

Copyright exists from the moment the work is created. You will have to register, however, if you wish to bring a lawsuit for infringement of a U.S. work.

https://www.copyright.gov/help/faq/faq-general.html

However, if it’s within 5 years of initial publication, they can still be granted a formal registered copyright and bring the complaint again.

(I mean it totally is) (the crochet community is much nicer)