 Selected special segments of the song will have glowing notes outlined by stars : successfully hitting all notes in this series will fill the " Star Power Meter " . The Star Power Meter can also be filled by using the whammy bar during sustained notes within these segments . Once the Star Power Meter is at least half full , the player can activate " Star Power " by pressing the select button or momentarily lifting the guitar into a vertical position . When Star Power is activated , the scoring <unk> is doubled until Star Power is depleted . The Rock Meter also increases more dramatically when Star Power is activated , making it easier for the player to make the Rock Meter stay at a high level . Thus , Star Power can be used strategically to play difficult sections of a song that otherwise might cause the player to fail . In the earlier entries of the series ( up until Guitar Hero : Aerosmith ) , activating Star Power meant that players could not <unk> more Star Power until the Star Power meter was fully drained and the effect ended . Starting with Guitar Hero : World Tour , more Star Power can be collected even if the effect is active by completing more Star Power phrases , extending the Star Power 's duration by doing so . When playing in cooperative play ( with a bassist / rhythm guitarist in Guitar Hero II through Guitar Hero : Aerosmith or as a band in Guitar Hero : World Tour ) , Star Power is shared between all the players and activation of Star Power is dependent on all players simultaneously activating it . 
