Embed album art into 1st track in folders only?

My album art is currently saved in album folders as folder.jpg. For itunes/ ipod reasons I'd like to embed art into the first track in each folder. Not necessarily all tracks numbered 1 though because for remixes and b-sides I tend to mark all tracks as track 1 so that they are listed alphabetically by mp3 players.

Any ideas?

Best to first decide what you mean by "first" track in each folder, and see if this criterion is supported by Mp3tag filter.