Denver symphony orchestra. Contract disputes Musicians file complaint with National Labor Relations Board. Post S 27, 1977 p.4 RMN S 27, 1977 p.6 Three year contract agreemnt not yet reached; three preseason concerts cancelled. I RMN S 20, 1977 p.6 Post S 20, 1977 p.30 Locked out of rehearsal; fails to reach agreement on new contract with management. RMN S 22, 1977 p.5