Diana Rigg
Actress Diana Rigg (right), who hosts “Mystery” on public television, talks to junior faculty in the Eliot House Library about the value of the voice as a teaching tool. Introducing her is Dorothy Zinberg, lecturer in public policy at the Kennedy School. (Staff photo by Rose Lincoln)

Some Harvard educators were the ones doing the listening last week when actress Dame Diana Rigg staged a brief demonstration on the proper use of theatrical vocal techniques.

“Voice has the capacity to hold an audience, to illuminate a text, or to spark imagination,” she told an audience of faculty and guests in the wood-paneled library at Eliot House.

The British actress, who hosts “Mystery” on public television, demonstrated several vocal exercises, including pitching the voice to the back of the room to be heard, using pauses to “snap your audience to attention,” and varying inflection.

Inflection can convey commitment, passion, and an interest in the subject, she said, while monotones are a sure way to fail. “It isn’t an optimistic way to address people,” she said. “Sooner or later it’s rather depressing.”

Rigg, known for her role in the 1960s TV series “The Avengers,” commented that politicians have long recognized the power of rhetoric and voice. Former British Prime Minister Margaret Thatcher took voice lessons because her voice was high and strident. Thatcher learned to use the deeper chest notes making her appear more authoritative and committed to her subject.

Joking that all politicians are insincere, Rigg said that the power of voice was such that it could make “their insincerity come across as sincerity.”

College professors, lecturers, and instructors must also make full use of their vocal talents to serve their purposes in the classroom, Rigg told her audience. “For those of you who speak regularly,” she said, “your voice and your body are there to serve your text.”