How does Leo’s perspective on McMurphy change throughout the novel as he gets to know that part of heritage?

For much of the novel, Melinda is Leo’s foil. What does it mean for a character to be a foil, and how does Melinda fulfil this role?

Much of the novel centers on music and Leo’s relationship with punk rock. How do characters like Leo, King Maggot, and Melinda explore this art form’s relationship to self-expression?