Don't look for opera posters, photographs or reviews on the walls of Mignon Dunn's Westside apartment. The Tennessee-born Metropolitan Opera star, one of the world's most sought-after mezzo-sopranos since the early 1970s, prefers to keep her two lives separate. She has no scrapbooks and saves no clippings. "I look forward to what I'm doing tomorrow," she explains. "I don't like those stand-up-and-sing roles. I loves to play wicked women. But you have to make them just as human as possible," she continues, her gold jewelry jingling as she settles onto the sofa. Tall and attractive, with large, expressive features, Miss Dunn is hospitality personified as she talks about her life and career over a glass of wine. This season at the Met she starred in both _Lohengrin_ and _Elektra_. In the spring she will appear in _Aida_ on the Met tour, and perform the role of Kundry in _Parsifal_ with Germany's Hamburg Opera. After that she plans some orchestral and opera concerts across the country. Long praised for her dramatic talents as well as her vocal skills, Miss Dunn has already signed contracts for performances into 1984. Although a few noted operas, such as _Carmen_, _Samson et Dalila_, and _Joan of Arc_, have a mezzo in the title role, most operas feature the higher-voiced soprano in the lead and a mezzo in a character role. "We may not have the main roles, but we have some of the best parts in _opera_," she says in her rich Southern accent, shouting the last word as if from an overflow of energy. "Not many of the roles I get today are angelic. It's often the 'other woman,' or the woman who causes the trouble." Married since 1972 to Kurt Klippstatter, a conductor and music director from Austria, Miss Dunn has never had any children of her own, somewhat to her regret. But she and her husband frequently have their nephews and nieces staying for extended periods. "Our niece Evi, from Austria, is living with us now. She's like a little daughter, and I adore her. She's 18, and she's going to go to nursing school." Mignon and Kurt are a very gregarious couple who enjoy throwing huge dinner parties. Mignon's cooking, like her singing, is international. "I cook Austrian. I cook New Orleans. I cook some nice Italian and French things. I'm going to be in Paris later this year for six weeks, and I really seriously want to go to the Cordon Bleu Cooking School, and take at least a three-week course." Around the late 1960s she was based in Germany for several years. There, says Dunn, many new operas are premiered each year, while in the U.S. they are a rarity. "It all comes back to the fact that we don't have government subsidy. We have to worry about selling tickets. Opera is an expensive thing, and until we get this government support -- which people for some reason are afraid of -- we cannot be as experimental as we would like to be."