According to the AP, Met audiences often reached 90 percent of capacity in the 1990s.
The company declined to comment on the memo.
The news agency also reports that the Met has made three hires as Volpe's tenure comes to an end. Coralie Toevs, a former New York Philharmonic fundraiser, has become director of development; Thomas Michel, who comes from the Public Theater, has been named director of marketing; and Elena Park, an executive at the public radio station WNYC, has been named director of communications.
Peter Gelb, the former president of Sony Classical, will replace Volpe in August.