MTV Games didn't pay $175 million for Harmonix Music Systems just for Rock Band. The studio also has at least one other project in development, as revealed by the programming guide for the 2008 Game Developers Conference.
Harmonix senior designer Chris Foster will be delivering a 60-minute lecture at the conference titled "Your Music is the Game: Designing the OTHER Project at Harmonix." (Emphasis in the original.) The session description explains that Harmonix has a history of creating "beatmatch" games in which users tap buttons or strum guitar controllers to match onscreen beats, but the studio's next project would be a bit different.
"Beats would not be authored by tech-savvy musicians," the description said of the next project, "but would instead be algorithmically generated, and the game would lack the dedicated peripherals that were critical to the success of the Guitar Hero series."
The purpose of the lecture is to share how the developers had to change or scrap parts of their established gameplay design in order to meet the needs of the new project. "Special attention is devoted to: the development of procedural gameplay algorithms; unique input mechanics; and triaging unexpected changes in scope and schedule."
Foster's bio on the site says that he's been handling the port of Rock Band to the PlayStation 2, and "on [TITLE DELETED], Chris has split his time between design and programming to bring Harmonix's patented music gaming to a new and uniquely cool platform." Over the course of 15 years in the industry, Foster has worked on massively multiplayer games such as Lord of the Rings Online: Shadows of Angmar and Asheron's Call, as well as the Lord of the Realms and Caesar strategy series.
The exact date and time of Foster's presentation haven't been finalized, but the 2008 GDC is scheduled for February 18-22 in San Francisco.