This one is fairly simple to achieve. You have to pass "Bohemian Rhapsody" as a band, with the minimum difficulty being medium. Simply set up 2 mics on a local game (one can be a Xbox 360 headset) and make sure they are both on medium. Start up the song and you shouldn't really have any troubles as medium vocals aren't that hard. Just as long as you sing into both mics and save star power for sections where you feel like you are about to fail. If you don't have 2 mics try finding someone to help out in the Achievement Trading Thread.