To program songs for the game, you or your developer friend first needs a membership to Microsoft's XNA Creators' Club, which was launched a couple years ago to let independent developers create casual games to sell through the Xbox Live Marketplace; a membership costs $49.99 for four months or $99.99 for a year. You'll then be able to get free tools and instructions from the Rock Band Creators Web site to convert your master recordings to the MIDI charts used by the game.