You can stack your Hero Power to a limited number of charges. Do not allow it to stack too full or it will be wasted. Hero Power temporarily boosts your score multiplier rate, past the normal x4 limit, allowing for better scoring opportunities during the heavy note parts of songs. Ensure that you are at the maximum score multiplier before using Hero Power. If you use it before your multiplier is at maximum, you will instead build it up at a faster rate.