Help finding software that will automatically identify and add metadata to my music?

I have a decade's worth of M4A music files (I can easily change them to MP3 with fre:ac though), mostly with custom names, no listed artist and non-existent metadata. If I wanted to automatically identify each song and attach metadata to as much as possible is there a program that I could use to go through it all, rather than going through 3000 files manually? Some of it was never released onto official music platforms, I suspect I'll have to work those ones out myself, but that's okay. I'd like it best if it were FOSS or open-source, but any suggestion would be helpful.