Christa Ludwig may be turning 89 tomorrow (March 16) but she shows no sign of losing her edge or her sense of humour. In a frank and wide-ranging interview with Christian Berzins for the Swiss publication NZZ on Sunday, the great German mezzo soprano talks frankly about her career and her art, while delivering the odd serve to the likes of Anna Netrebko and Fritz Wunderlich.

“Nowadays, in the supermarket, when somebody approaches me and says: ‘You gave me so many happy hours,’ I begin to cry. That’s what moves me, that’s the only thing that counts,” she says, beginning with what might seem a sentimental exchange. But she soon toughens up, humbly dismissing her career as “so-called”. Although she might admit that she’d had the odd “beautiful” moment in performance, she rapidly dismisses such thoughts as “egoism”, and when the interviewer suggests that performers seek admiration from audiences, replies: “No, for God’s sake! That would be terrible.”

Unusually, for a famous opera singer, she admits that opera never really interested her with the possible exception of Wagner or Strauss. “But all the Italian operas of Rossini, Donizetti, and Verdi: Is that really art?” she says. Asked about colleagues she admired, she replies “actually, none”, but makes something of an exception for the late Jon Vickers and Maria Callas. “When Jon Vickers sang ‘Gott, welch Dunkel hier’ [God, what darkness here – in Fidelio], I began to weep on the stage,” she says. “This had nothing to do with beautiful singing, that was expression… If, on the other hand, I hear the stretta from Il Trovatore with the high C, I am delighted, but I do not admire him. Callas is probably the only one I admire: her voice was the tragedy of her life.”

She’s less kind about the respected tenor Fritz Wunderlich, a singer with whom Ludwig occasionally performed. “At that time he was a stupid boy full of stupid jokes,” she says. “We were singing some mass, and he had squashed some orange peel between his teeth like children at school. When I was standing beside him, I did not feel very much.” She also takes him to task for what she believes to have been marital infidelity.

Responding to a question about fame, she gently mocks operatic rivalries: “Of course, you can listen to who has more applause. And it depends on how one receives that applause: drop to the knees, let the long hair fall on the stage, for hours, arms up, the people scream – then one gets up quite slowly. This is great art.”

She’s also refreshingly frank about her career lows, in particular the 1975 Salzburg Festival. “I was in the middle of a divorce and the menopause and had capillaries bursting on my vocal chords. Everything happened together. I sang the high notes badly, left the city and fell into a depression…. In retrospect it was a blessing: otherwise I would have sung these great heavy soprano parts for ever and the voice would have been ruined.”

When asked if she’d ever wanted to become a ‘star’, she replies that it isn’t something one thinks about, one just becomes it, adding that she believes she was lucky that her ‘rivals’ at the time were either too old or too young. She also insists that there is no such thing as the best. “If today it is said that Netrebko, who has a lot of advertising, is the best opera singer in the world, this is not true,” she declares. “Apart from Netrebko there are many that are not known. In five years we will have another Netrebko.”

She also has some advice for young singers. “You can sing the wrong roles, or a woman can have a child too early, which is nonsense for the career,” she says. “As a singer one must wear blinkers. A stupid singer can still make a career. But that is so difficult! Look at Maria Callas – she did not have a nice voice, but what she made of it, these interpretations – incredible! When Callas sings a Bellini recitative, I begin to cry. But sometimes you cannot describe what a singer has or does not have. Is it called charisma? Or personality? ‘It’s a secret,’ my mother always said. I do not know if I had that secret aged 20.”

Ludwig admits that she stopped singing when she felt she could no longer compete with herself. “I noticed that some of the sounds were not as they were,” she says. “There are others who cannot stop. Plácido Domingo will soon be singing Sarastro. What’s the point of that? Or does he have nothing but the music? I find it sad when one cannot get away from work – it is ridiculous.”

As a professional, although she felt committed to singing, it did come at a cost. “My vocal cords and I could not go to a restaurant after a premiere, so I’d leave. But that is not deprivation, it is self-evident that one wants to live for the profession. However, this depends on the human being… my first husband Walter Berry had to have people around him. My body could not stand it. But then my husband could not bear liver sausage and spinach… I would never be a singer again.”

And her choice of funeral music? “Ich bin der Welt abhanden gekommen (I am lost to the world) from Gustav Mahler’s Rückert Lieder… please sung by me! But I do not know yet which recording… No, I am serious!”