The standards applied are exactly the same regardless of what tools are used. It doesn't matter if you're talking about a dumb AI, a general purpose AI, or a Xerox machine.
If you want an exception to copyright, you're going to want to start looking at a section 107 (of the copyright act) exception: https://www.copyright.gov/title17/92chap1.html#107
The reason someone walking down the street and humming a song is not a violation is because it very clearly meets all of the tests in section 107.
The biggest problem with feeding stuff through a black box like an LLM is it isn't easy for a human to determine how close the result is to the original. An LLM could act like a Xerox machine, and it won't tell you.
