Little Heroes by Norman Spinrad.
Bantam Books. Paperback reissue. 1992. 563pp.
From Library Journal:
"An over-the-hill rock star, a Puerto Rican street kid, and two children of the electronic age discover strength in numbers when they take on the power of Musik, Inc., in a war of nerves, passion, and rock 'n' roll. Spinrad ( Child of Wonder ) uses the violent, sexually explicit language of new wave sf to communicate an ultimately touching message of courage and humanity that breaks through the high-tech glitter of his medium. Recommended." JC