Sentence Correction

Except for a concert performance that the composer himself staged in 1911, Scott Joplin's ragtime opera
Treemonisha was not produced until 1972, sixty-one years after its completion.

(A) Except for a concert performance that the composer himself staged
(B) Except for a concert performance with the composer himself staging it
(C) Besides a concert performance being staged by the composer himself
(D) Excepting a concert performance that the composer himself staged
(E) With the exception of a concert performance with the staging done by the composer himself

OAA

Why THAT in option A for what purpose?

I think that is a relative pronoun referring to concert performance
"that" introduces the essential middle modifier " that the composer himself staged in 1911 "