The below description is taken from LEGO.com.
“Shock and roll, my rockin’ monsters!”
One day, the Monster Scientist heard about the cool hand-made monsters that all of the other mad scientists were building, so he decided to try putting together his own. He thought that he had gotten the recipe right, but some of the music he was listening to must have fallen into his creature creation’s head, because what he got was the ultimate rock ‘n roll monster!
The Monster Rocker gets a real charge from rocking – literally! The more he rocks out on his guitar, the more electricity he generates, making him his own power supply and amplifier in one. When he really gets into the ghastly groove, his creepy chords can wake up the Gargoyle, set the Wolf Guy’s hair on end, and even get the Zombies tapping their toes!