I've tried to apply the following advice on the flac files:
for x in *.flac; do
ffmpeg -i "$x" -map 0:a -codec:a copy -map_metadata -1 clean_"$x";
done
But it seems, that ffmpeg though removes most metadata, it also adds its own fingerprint.
Why does it add this tag? What is the best way to get rid of it?
