%n. %a - %t

Strings associated with code    Will fill the field
%a
  Artist
%b
  Album
%c
  Comment
%p
  Composer
%r
  Copyright
%e
  Encoded by
%g
  Genre
%i
  None! (used to ignore a string)
%l
  Number of tracks
%o
  Original artist
%n
  Track
%t
  Title
%u
  URL
%y
  Year

“/mnt/MP3/EVANESCENCE – Fallen (2003) – Rock/01. Going Under.mp3”

b) with the pattern :

“%a - %b (%y) - %g/%n. %t”

c) you will fill the tag with theses strings :

    Artist (%a) => EVANESCENCE
    Album (%b) => Fallen
    Year (%y) => 2003
    Genre (%g) => Rock
    Track (%n) => 01
    Title (%t) => Going Under

for x in *.mp3; do
  TITLE=$(strings "$x" |grep TAG |grep -v TAGL |sed "s/^.*TAG//g ; /^L$/d ; /^@$/d ; /^$/d ; /^Ac$/d")
  #mv "$x" "$TITLE.mp3"
  echo $x" "$TITLE.mp3" #just echo for now, until further tested
done

sed -i "s/$TITLE/$x/" "$x"

for i in *.mp3; do avconv -y -i "$i" -c copy -metadata title="$i" new_"$i"; done;

for i in *.mp3; do /your/venv/bin/eyeD3 --title "$i" "$i"; done