Tag Editor supports tags for MP3, AIFF, WAV, FLAC, MP4 and M4A (Apple lossless) files, namely:

Files' format
Accepted tags' formats
Modified tags are saved in formats

MP3

ID3v1, ID3v2 ID3v2

AIFF

ID3v2 ID3v2

WAV*

ID3v2, Info

ID3v2 and Info

FLAC*

XIPH, ID3v1, ID3v2

XIPH (ID3v1 and ID3v2 are synchronized with XIPH if they are present in the file).

MP4, M4A

MP4 MP4

* - iTunes and Finder don't support metadata in WAV and FLAC files. iTunes also does not support FLAC files in any form.

Modified text tags are saved in Unicode/UTF8 format.

If some of your files are not supported by Tag Editor, you can convert them to suitable audio format with To Audio Converter for Mac >>.