Flac-utils is a toolkit for managing FLAC files. Its primary usage is syncing metadata between sets of FLAC files. Flac-utils also provides a Python module called flac_compare that can be used separately. The utilitiy consist of three tools: flac-sync, which syncs a file tree of FLAC comments for files with the same audio-part; flac-diff, which compares two FLAC files' metadata information and shows the differences; and flac-add-picture, which adds album cover art to the files using Amazon.
SQL Tagger reads the tags of audio files from a directory, loads them into a temporary SQLite database, accepts SQL queries to modify this database, then saves any changes back to the audio files. It's useful for performing complex updates that would be difficult or tedious with conventional taggers. It's a complement to conventional taggers, not a replacement.