It would have been easier to solve the problem by using a more handy scripting language.
Dano, see attached command file.
DD.20110116.2135.CET
Sorry, I did forget to include the most important case:
The folder with music files but without folder.jpg.
Attachment 3580 not found.
DD.20110116.2300.CET
Edit. Attachment removed.
DD.20110117.1747.CET