I can run legally an mp3 through a calculator. No one can dictate otherwise - it's my machine, and purchased media to do with as I (privately) please. This does not interfere with copyright. To legislate otherwise would be insane - as that would effectively legislate your ability to calculate.
This argument extends to any purchased media, to any program.
unless i’m mistaken, nobody is telling you what to do with your media.
the issue at play here would be whether the emulator publishers/developers have the right to publish what is almost certainly an infringing piece of software, which courts have repeatedly determined they do not.
If your mp3 is copy protected and your calculator bypasses that copy protection, it is in fact illegal (in the US)