these files are either exactly the same as, or somehow worse than, the stuff in the parent folder

neat oneliner to compare the audio contents of files (so the checksum is not affected by tags or embedded cover art):

while IFS= read -r x; do ffmpeg -hide_banner -nostdin -i "$x" -f framemd5 - | awk '/media_type [0-9]: audio/{sub(/:.*/,"");sub(/.* /,"");tgt=$1 ","} $1==tgt{sub(/[^,]+/,"");print}' | shasum; echo; done

sdafasdfdsfasadf