How to stop my Mac from cloning MP3 files on my USB stick?
If you delete them manually a lot of them will reappear at eject. .DS_Store, trashes, fseventsd &amp; spotlight files especially.

There have been a number of software solutions over the years, most only partially successful. BlueHarvest was about the best I'd tried until recently, but wasn't 100% effective.

I'm currently testing CleanMyDrive, freeware, though they are using it as a bit of an advert for CleanMyMac for your internal drives, but you can ignore that. So far it seems to be fairly effective, but still misses the trash files every so often.