Any music apps that have built in automatic tagging via online music databases?

Good question. I'd like to also know the answer. Often, I find its not until I am in a music player on one of my devices that it becomes clear that a track or album, or some other tag or artwork is missing or didn't take. Having a tag editor built into a player would be useful, in my opinion.
 
Yeah I agree that it is easier if doing bulk files from on a laptop/PC. I always used to just use Windows Media Player from an entire library perspective. The use-case I was thinking of was more for one-ofs here and there, without needing to hook up to laptop/PC and retransfer new versions of the files. The risk of course is then libraries also get out of sync.