while read -d $'\0' file; do
   [ -f "$file" ] || continue
   
   newname=${f//[^a-zA-Z0-9_.]/_}
   
   [ "$file" = "$newname" ] && continue
   [ -f "$newname" ] && continue
   
   echo "$file" 
   echo "$newname"
   echo "________________________________"
done < <(find . -type f -print0)

if I replace echo by mv then I get errors like this:
mv: cannot move `./audio/hafez/Abdel_Halim_Hafez_-_Ahwak.mp3' to `': No such file or directory


here is the ouput:
./audio/hafez/Abdel_Halim_Hafez_-_Ahwak.mp3

________________________________
./audio/hafez/Abdelhalim_Hafez_-_Gabbar.mp3

________________________________
./audio/hafez/Abdel_Halim_Hafez_-_Asmar_Ya_Asmarani.mp3

________________________________
./audio/hafez/Abdel_Halim_Hafez_-Musica_Arabe_-_Bahlam_Beek.mp3

________________________________
./audio/hafez/abdelhalim_hafez_jana_l'hawa.avi