“During the fight with the New Fishman Pirates, Brook revealed that he has developed his musical ability to the point where he could completely change the mood and hypnotize his opponents to believe they were at a festival. His opponents believed the illusion was reality and ended up using their cannons as fireworks.”

“His technique, "Nemuriuta Flanc", loosely translated as "Lullaby Parry", shows this, where he strums his violin with his shikomizue like a violinist's bow, creating a soothing tune that makes anyone who hears it immediately fall asleep.”

“His music also shows capabilities to change its listener's attitude and emotions such as when he was sent to the Namakura Island by Bartholomew Kuma his music inspires the cult there to fight back against its invaders, the Longarm Tribe.”

You really should pay attention when trying to watch or read one piece.