With the success of Guitar Hero another game is in the works by Harmonix (who were the original developers behind the Guitar Hero franchise, which has since been pawned off to Tony Hawks developers Neversoft.) They have worked on a seperate game instead known as 'Rock Band'. Seems that the rumours have suggested that Microsoft might have got their hands on a limited exclusivity deal for the title. However this is just rumour and speculation at the moment.
Read whole article here:
Rock Band struts onto 360 first? - CVG.com
Read whole article here:
Rock Band struts onto 360 first? - CVG.com