Jojo McDodd is a timid and shy boy with a penchant for music. He is the oldest child of the Mayor of Whoville. His father, Ned, and mother, Sally, are both proud of his accomplishments. However, JoJo doesn't want to follow in his father's footsteps.
As a child, JoJo studied at the Wholliard. He also collected odd objects found around the town. One of these items was a large instrument made of castaway objects. It was called the "Symphonophone," and helped Whos make noise in their own town.
Then, when JoJo was six years old, a terrible tragedy struck his family. He lost his father. This tragedy changed JoJo's personality. Instead of following in his father's footsteps, he wanted to pursue a musical career.
Although Horton is a good friend, he is not willing to give up on JoJo. When he is threatened, he is able to hear a voice that tells him the speck is a Who. Since then, he has been working to protect the city of Whoville.
In order to help, JoJo sets up a complicated system to produce music. At night, he sneaks up to the abandoned observatory. Eventually, he reaches the top of the speck and grabs the horn that projects the voice. Despite the obstacles, he is able to penetrate the surface of the speck, scream his first word, and break the sound barrier.
Once he screams, he finds that his voice isn't the only one who is able to make music. Other Whos, like Morton and Yummo, also have a voice.