Music has shown to foster and promote self-esteem in children of all ages. My second grader began taking kinder music class at the age of 3 1/2 and piano lesson for two years now, I've seen him grow so much. His social skills have improved and his academic skills (particularly his math knowledge) have soared. In all, I think introducing children to music makes them a more rounded person.
Below are articles on the benefits of music and building self-esteem in children.