Karaoke Revolution

This can probably be done with Nothing but a good Time and Host with the Most at the same time but I didn't see these in time to group them so I had to do them separately. Anyway, I got this just by going into party mode and adding one AI character to the party. Next you need to create a team and give it a a name. I just saved the default name, Team 1. Put both you and the AI on the same team and choose any mode, I chose the short 3-song mode. When I started the game it defaulted to co-op. I sang for both myself and the AI. After the final save the achievement will unlock.