"know the score"--1887 attestations in opera context

[Cohen, Gerald Leonard]

Making of American (Cornell) has just one item for "know the score", with the attestation being in an opera context:
   "Wagner and Scenic Art," by William F. Apthorp,  in _Scribner's Magazine_,
vol. 2,  no. 5, Nov. 1887, pp. 515-532. The relevant page is 528:
        "...The anecdote I told about Lohengrin at the beginning of this article is a fair example of what I mean. [G. Cohen: an actress did not know the score and,  upon being startled by a blast of trumpets, made a dramatic scene look a bit ridiculous.]  It is not enough for the singing actor to know the text and music of his own part in the scene; not enough, even for him to know the parts of those who play with him;  HE MUST KNOW THE ORCHESTRAL SCORE OF THE SCENE [G.Cohen: my caps.]--or,at worst, the piano-forte transcrption thereof--by heart. The Wagnerian actor who DOES NOT KNOW THE SCORE [G. Cohen: my caps.] of all the scenes in which he takes part is in as bad a case as the pianist who knows only the solo part in the concerto he is to play.  This complete knowledge is necessary not merely to insure the perfection of certain realistic details,... It is necessary for a far more important purpose--the actor's by-play is often to be regulated by what music is going on in the orchestra. ..."

Gerald Cohen