Say last year at your school you made $65K. Then when your contract is up for renewal, the school board says that they'll give you a new contract...but will only pay you state minimum. Only a fool would agree to that new contract...anyone else would air up the tires and move on.
Did the orchestra board hold a gun to the musicians' heads and assure them that either their brains, or their signatures would be on the contract? No...as you stated they willingly accepted that salary. Sorry, but this is on the musicians; they negotiated themselves into that hole.