They don't seem to be attempting to prevent him from publishing his music. They will just revoke parole if he violates their terms. They're not suppressing speech. They're giving him supervised release on condition.

Officially, it exists; in practice, behavior is so regulated it’s not worth much. My point is that it’s more of an “on paper” free speech in comparison to a non-incarcerated individual.

Since they can put you in solitary confinement or beat you up for speaking