What in-game power can double the score multiplier in Guitar Hero?

Star Power is the in-game power that can double the score multiplier in Guitar Hero.

Players earn Star Power by completing special phrases marked with glowing notes; using the whammy bar on sustained notes in those phrases can also fill the meter. Once the meter is at least half full, the player can activate the power by tilting the guitar or pressing the appropriate controller button.

While active, Star Power doubles scoring and makes the Rock Meter rise more quickly, so it can rescue a player during a difficult section. It is not the same as the ordinary multiplier earned by hitting consecutive notes: that multiplier builds through normal play, while Star Power is a temporary strategic boost.

Later Guitar Hero games expanded how the feature worked, including allowing players to collect additional Star Power phrases while the effect was already active. In related spin-offs, the equivalent ability may have a different name, such as Euphoria in DJ Hero, which is a common source of mix-ups.