Curtain raiser

A curtain raiser is a performance, stage act, show, actor or performer that opens a show for the main attraction. The term is derived from the act of raising the stage curtain. The first person on stage has "raised the curtain".

The fashion in the late Victorian era and Edwardian era was to present long evenings in the theatre, and so full-length pieces were often presented together with companion pieces. Each full-length work was normally accompanied by one or two short companion pieces. If the piece began the performance, it was called a curtain raiser. One that followed the full-length piece was called an afterpiece. W. J. MacQueen-Pope commented, concerning the curtain raisers:

...
Wikipedia