add m4a files to iTunes from directory tree in AppleScript

addFiles.applescript

set src to choose folder
set target_files to getFiles(src)
tell application "iTunes"
	repeat with f in target_files
		try
			add f
			delay 1
		on error
			log f
		end try
	end repeat
end tell

on getFiles(target_folder)
	tell application "Finder"
		tell folder target_folder
			set tmp to {}
			log "called"
			set m4a_files to (get every file of target_folder whose file type is "M4A ")
			repeat with f1 in m4a_files
				set end of tmp to f1 as alias
			end repeat
			
			set f_list to (get every folder of target_folder)
			repeat with f2 in f_list
				set ans to getFiles(f2) of me
				if (count of ans) is not 0 then
					set tmp to tmp & ans
				end if
			end repeat
			
			set result to tmp
			
		end tell
	end tell
end getFiles