Add mp3 to iTunes, delete file from Downloads, add Comment?

Question

I'm trying to make a folder action that will:
- Watch my 'Downloads' folder for downloaded .mp3 files.
- Add those .mp3 files to iTunes, letting iTunes copy to music folder.
- Delete the original file from the 'Downloads' folder.
- In iTunes, append '#single' to the Comment field of added .mp3.
So far I have the first three working, but cannot get it to append the #single part to the Comment field, here's what I have:
property myFiletypes : {".mp3"}
on adding folder items to this_folder after receiving added_items
set myFinderItems to added_items
tell application "System Events"
set allItems to every item of myFinderItems
end tell
repeat with i from 1 to the count of allItems
try
-- get an item
set myFinderItem to (item i of allItems as alias)
-- check if it is a folder
tell application "Finder" to set myItemIsFolder to (kind of myFinderItem = "Folder")
-- if it isn't a folder...
if myItemIsFolder is false then
-- see if the file has the right extension
tell application "Finder" to set myItemExtension to "." & (name extension of myFinderItem) as string
if myFiletypes contains myItemExtension then
set mySongName to myFinderItem as alias
-- add track to iTunes
tell application "iTunes"
add mySongName
end tell
tell application "Finder" to delete file myFinderItem
end if
end if
on error
display dialog "Error"
end try
end repeat
end adding folder items to

Answer 1

Better yet, an Applescript that can be used as a folder action to watch the Downloads folder and:
1) Open .mp3s in iTunes and append #single to track Comments, then delete original .mp3s.
2) Open .zip and .rar archives, parse then unarchived folder for .mp3 files, add them to iTunes, append #album to track Comments, then delete original folder of .mp3s.
2a) Bonus points if the script adds the .mp3s to itunes in descending order based on file name track numbers (track 10, track 9, track 8...).