Apple Music converted my MP3 files to M4a - Why??

Have you ever had a subscription to either Apple Music or iTunes Match? If so, did you use this subscription to migrate your library from one computer to another? Tracks matched with the Apple Music catalog will typically download as 256k AAC files when downloaded to another computer, or after freeing up local space using the Remove Download option, and then later downloading to use locally.

tt2

The only thing I can think of is that at some point iTunes or Music wasn't respecting your preferred import method, but you didn't notice it at the time. Those settings wouldn't have transferred from iTunes to Music. I've already discussed the only other possible mechanisms I can think of that would result in a change of format after music has been ripped to your computer, which don't seem to apply.

tt2

bOMBfACTORY wrote:

I guess I'm just kind of offended that Apple would, without asking for approval, reach into my personal computer and modify my files.

This isn't a thing that happens. iTunes Store purchases are .m4a, and matched items downloaded from an Apple Music/iTunes Match subscription would be. CD rips might default to .m4a on first install. iTunes for Windows has a feature to convert .wma tracks to .m4a files (as copies) on import. Nothing else in Apple Music or iTunes is designed to modify the format of files attached to the library. The closest is a feature to make new copies of existing files in a different format. See Convert a song to a different file format with the Apple Music app or iTunes for Windows - Apple Support.

tt2