Questions of editions and orchestration aside, Modest Mussorgsky's penetrating, powerful and potent four-act Boris Godunov, arguably the greatest Russian opera of the 19th c., requires no less than a figure of towering stature to portray this late 16th - early 17th c. Russian Czar. This 1958 Covent Garden performance led by Czech conductor Rafael Kubelik, in his last year as the Royal Opera House music director, has such a figure in Boris Christoff, a bass of considerable vocal and acting talent. Josephine Veasey, Geraint Evans and Regina Resnik, among other cast members, prove no less formidable.