Select tracks in iTunes and this script will search for tracks metadata from iTunes stores and apply metadata to track. <http://forums.macrumors.com/showthread.php?t=1275897> // added 'spanish' support

itunes_match_meta.rb

#!/usr/bin/env ruby
# reviewed by Erik B on January 21 2012
# by @tapbot_paul
# Don't blame me if this nukes your metadata, formats your drive, kills your kids
# This script goes through any iCloud Matched songs in your iTunes library and tries to update the
# metadata from the iTunes Store
# Will run against selected tracks or if nothing selected entire library
# install the required gems with the following commands
# sudo gem install json --no-ri --no-rdoc
# sudo gem install rb-appscript --no-ri --no-rdoc
# then run the script with "ruby meta.rb"
require 'rubygems'
require 'appscript'
require 'json'
require 'open-uri'

class Track
   attr_reader :iTunes_id
   attr_reader :iTunes_track
   def initialize(iTunes_track)
      @iTunes_track = iTunes_track
      path = @iTunes_track.location.get.path
      file_string = File.open(path, 'r').read(1024) # data always seems to be around 600-700 bytes in
      index = file_string.index('song')
      if index
         @iTunes_id = file_string[index+4,4].unpack('N')[0]
      else
         puts "Couldn't find @iTunes_track id #{iTunes_track.name.get}"
      end
   end

   def valid?
      @iTunes_id.nil?
   end

   def update_track(result)
      @iTunes_track.name.set(result['trackName'])
      @iTunes_track.album.set(result['collectionName'])
      @iTunes_track.artist.set(result['artistName'])
      @iTunes_track.track_count.set(result['trackCount'])
      @iTunes_track.track_number.set(result['trackNumber'])
      if result['primaryGenreName'] != nil
         @iTunes_track.genre.set(result['primaryGenreName'])
      end
      @iTunes_track.disc_count.set(result['discCount'])
      @iTunes_track.disc_number.set(result['discNumber'])
      @iTunes_track.album_artist.set(result['artistName'])
      if result['releaseDate'] != nil
         releasedate = result['releaseDate']
         releaseyear = releasedate[0..3]
         @iTunes_track.year.set(releaseyear)
      end
   end

end

WORK_SIZE = 100
STDOUT.sync = true
tracks = []

app = Appscript.app.by_name("iTunes")

iTunes_tracks = app.selection.get
if iTunes_tracks.count == 0
   iTunes_tracks = app.library_playlists[1].tracks.get
end

print "Reading #{iTunes_tracks.count} tracks "
iTunes_tracks.each do | iTunes_track |
   begin
      if iTunes_track.kind.get == 'Matched AAC audio file' or iTunes_track.kind.get =='Fichier audio AAC mis en correspondance' or iTunes_track.kind.get == 'Fichier audio AAC' or iTunes_track.kind.get == 'Abgeglichene AAC-Audiodatei' or iTunes_track.kind.get == 'Archivo de audio AAC coincidente'
         # or iTunes_track.kind.get == 'Fichier audio AAC acheté'
         # triggers an invalid multibyte char (US-ASCII) on the 'é'
         
         track = Track.new(iTunes_track)
         print "Track #{track}"
         unless track.valid?
            tracks << track
            print '*' if ((tracks.count % WORK_SIZE) == 0)
         end
      end
   rescue StandardError => e
      puts e
   end
end
puts ''

# all 2 char countries codes lots currently not valid %w(AF AX AL DZ AS AD AO AI AQ AG AR AM AW AU AT AZ BS BH BD BB BY BE BZ BJ BM BT BO BQ BA BW BV BR IO BN BG BF BI KH CM CA CV KY CF TD CL CN CX CC CO KM CG CD CK CR CI HR CU CW CY CZ DK DJ DM DO EC EG SV GQ ER EE ET FK FO FJ FI FR GF PF TF GA GM GE DE GH GI GR GL GD GP GU GT GG GN GW GY HT HM VA HN HK HU IS IN ID IR IQ IE IM IL IT JM JP JE JO KZ KE KI KP KR KW KG LA LV LB LS LR LY LI LT LU MO MK MG MW MY MV ML MT MH MQ MR MU YT MX FM MD MC MN ME MS MA MZ MM NA NR NP NL NC NZ NI NE NG NU NF MP NO OM PK PW PS PA PG PY PE PH PN PL PT PR QA RE RO RU RW BL SH KN LC MF PM VC WS SM ST SA SN RS SC SL SG SX SK SI SB SO ZA GS SS ES LK SD SR SJ SZ SE CH SY TW TJ TZ TH TL TG TK TO TT TN TR TM TC TV UG UA AE GB US UM UY UZ VU VE VN VG VI WF EH YE ZM ZW)

countries = %w(US FR GB AU DE CA IT JP DZ AO AI AG AR AM AT AZ BS BH BD BB BY BE BZ BM BO BW BR BN BG CM KY CL CN CO CR CI HR CY CZ DK DM DO EC EG SV EE ET FI GH GR GD GT GY HN HK HU IS IN ID IE IL JM JO KZ KE KR KW LV LB LY LI LT LU MO MK MG MY MV ML MT MU MX MD MS MM NP NL NZ NI NE NG NO OM PK PA PY PE PH PL PT QA RO RU KN LC VC SA SN RS SG SK SI ZA ES LK SR SE CH TW TZ TH TT TN TR TC UG UA AE UY UZ VE VN VG YE)

puts "Found #{tracks.count} matched tracks"
countries.each do | country |
   print "Querying #{country} store for #{tracks.count} tracks "
   counter = 0
   tracks.dup.each.each_slice(WORK_SIZE) do | subtracks |
      ids = subtracks.map { | track | track.iTunes_id }
      #iTunesHash = JSON.parse(open("http://itunes.apple.com/lookup?id=#{ids.join(',')}&country=#{country}").read)
      iTunesHash =JSON.parse(open("http://ax.phobos.apple.com.edgesuite.net/WebObjects/MZStoreServices.woa/wa/wsLookup?id=#{ids.join(',')}&country=#{country}").read)
      print '*'
      iTunesHash['results'].each do | result |
         result_id = result['trackId']
         subtracks.each do | track |
            if result_id == track.iTunes_id
               track.update_track(result)
               tracks.delete(track)
               counter += 1
               break
            end
         end
      end
   end
   puts " #{counter} updated"
   break if tracks.empty?
end

puts "Couldn't find metadata for #{tracks.count} tracks" if tracks.count != 0

I'm happy to see this version handles year and also handles nil results. I haven't run into a lookup that in which primaryGenreName is nil so it may not be necessary to check, but it doesn't hurt. But collectionArtistName is usually nil unless it's different than artistName , so a nil check can be used to get the album artist value from the iTunes Store when it exists and fall back on using the track artist otherwise.

Change
@iTunes_track.artist.set(result['artistName'])
to
if result ['collectionArtistName'] != nil
@iTunes_track.album_artist.set(result['collectionArtistName'])
else
@iTunes_track.album_artist.set(result['artistName'])
end

Another change I've found useful is adding &lang=en_us to the iTunesHash lookup URL to get all countries' results in U.S. English. (For your own language, change en_us to your language and country code.)

@NemWan are you still able to use this with iTunes 12? If so, how? I'm unable to retrieve matched songs.

Thanks.