Fe w singers today can boast a career to match Christa Ludwig. Although she retired in 1994 – these days “I don’t even sing with my dog,” she jokes – the great German mezzo who celebrated her 90th birthday on March 16 is still actively involved in masterclasses and has been happily giving opinion-filled anniversary interviews.

Christa Ludwig at 90

Born in 1928 into a musical family in Berlin, Christa Ludwig’s father Anton was a tenor, director and opera administrator while her first teacher was her mother, Eugenie Besalla-Ludwig, a mezzo-soprano who sang under Karajan at the Aachen Opera. “Once I fell in love with my chemistry teacher at school and I wanted to study chemistry, otherwise I was always passionate about singing,” she explains.

Passing a veil over any impact that Hitler’s Germany might have had on her education – “I was a child during the war and went to school,” she says – Ludwig made her professional debut aged 18 in Frankfurt as Prince Orlofsky in Die Fledermaus. “I had a voice and I was engaged. I was not ready, but I needed the...