Harmonix and MTV are bringing Rock Band to Japan with some help from Tetsuya Mizuguchi's Q Entertainment (Lumines). According to the press release, "The two studios will work together to develop the title, marking the first US-originated rock music game to be heavily localized for the Japanese market." No clue on what that heavy localization will entail.
It has been little over a week since a Harmonix rep was asked about the possibility of seeing Japanese content in Rock Band. At the time, the rep said an official announcement on future DLC plans would arrive in "a little over a week." So, the question remains: How does one program instrument tracks for a Genki Rockets song?