Guitar Hero World Tour

While in a four player band you will all need to have a 4x multiplier at the same time, then all use active star power at the same time. It doesn't have to be deployed all with-in the same second, but rather all of your individual instruments need to be in active star power in the same time period while still maintaining a 4x multiplier, which will in turn become a 8x multiplier. Which means you'll need to build your star power for all four players to have enough to use.