convert_audio () {
    target_dir=$HOME/Documents/recordings
    filename="$(date -r $1 +%F_%T.mp3 | tr ':' '-')"
    ffmpeg -i $1 $target_dir/$filename
    rip $1
}
export -f convert_audio

sudo mount -o uid=1000,gid=1000 /media/rec
find /media/rec -name \*.WMA -exec bash -c 'convert_audio "{}"' \;
sudo umount /media/rec