In the screenplay Sweethearts, Victor Herbert's play was was used. What type of performance was this?
Sweethearts (1938 film):  The screenplay, by Dorothy Parker and Alan Campbell, uses the “play within a play” device: a contemporary Broadway production of the 1913 Victor Herbert operetta is the setting for another pair of sweethearts, the stars of the show. Victor Herbert: Victor August Herbert (February 1, 1859 – May 26, 1924) was an Irish-born, German-raised American composer, cellist and conductor.
“play within a play”