Senior designer Brian Chan outed the news in his resume — though other than the project's existence, details are unsurprisingly scarce.
The studio said in a statement to Joystiq: "As we've stated before our studio is growing and hard at work on a variety of titles. In a storied Harmonix tradition, our designers start working on those games before they're publicly announced."
The developer continued that it would have more information "in the coming months, probably via a LinkedIn update or something - we haven't decided". Now that's the kind of humour we can get behind.