The series has also been criticized for its release model in contrast to the Rock Band series, causing some players to hold contempt towards Activision.[212][213] Harmonix considered the Rock Band series as a "music platform", and supported it with downloadable content and the ability to import songs from its games and expansions into most other games of the series.[214] Critics argued that Guitar Hero should have been doing the same, either through releasing expansions that could be incorporated into the main games of the series, or by issuing the songs as downloadable content.[215][216][217][218] The release of Guitar Hero: Smash Hits, reworking older songs from the series to full four-instrument band support but otherwise adding no additional material, was called "the definition of 'milking'" by reviewers, with no observable technical limitation as to why the songs could not be added as downloadable content.[212][216][219][220][221] Ars Technica recognized that licensing issues might have limited when songs from one single game could be played in others of the series (such as the case for The Beatles: Rock Band), but that such cross-compatibility should have been a high priority for rhythm games.[222] Furthermore, some expansions were praised for the additional content beyond the note-matching gameplay; Guitar Hero: Metallica is considered to be one of the series' best works to be developed by Neversoft in part due to the care that the developers took with imaging the band and the available extras for the game.[215] Activision later revealed that both Guitar Hero 5 and Band Hero would support playing songs from both Guitar Hero World Tour (both on-disc and downloadable content) and Guitar Hero Smash Hits, with music licensing being the only limiting factor on which songs could be made forward-compatible.[103]