Dance Dance Revolution ULTRAMIX, or DDR Ultramix, is the sixth home version of Dance Dance Revolution to be released in the United States, and the first DDR game to be released on the Microsoft Xbox video game console. It was released by Konami exclusively in North America on November 19, 2003, being the first ever DDR game exclusively for the American audience. A European version called Dancing Stage Unleashed was released shortly after. It comes with 51 songs, nine of which are hidden and unlockable. 15 of those songs were new to Dance Dance Revolution.
Source: Wikipedia, "[ http://en.wikipedia.org/wiki/Dance_Dance_Revolution_Ultramix Dance Dance Revolution Ultramix]", available under the [ http://creativecommons.org/licenses/by-sa/3.0/ CC-BY-SA License].