Let's get one thing straight: there is *no* online community for this game. However, luckily for you, EA doesn't own this game. That means that it's still possible to get it, even if you have to bribe someone to do it with you. The other alternative would be to have two Xboxes.
Assuming you *can* find someone, all of the online achievements can be boosted in 20 minutes. For this one, load up the American Idol multiplayer, choose Ranked, and pick a song. Both people need to play the whole song to count.