Legal Question in Entertainment Law in California

No, the manager can't tell the musician s/he cant work until the dispute is resolved. If it's later determined that the musician is in breach, s/he may end up having to fork over some money to the manager based on the terms of the agreement, though.

California is a right to work state, so the musician should still be able to work. Take a look at the contract between the parties to look for applicable language, but anything trying to restrict the musician's right to make a living probably won't be enforced by the courts, as it is against public policy.