She studied music at the Conservatorium van Amsterdam and worked in a small bookshop. He studied art in Amsterdam and Paris and worked as an art teacher.
They met when a friend of his moved into her building in Staastraat, a canal-side street in Amsterdam, in the early 1950s. It was love at first sight and a meeting of minds, says Leo Cappel. It is a love story the writer of several manuals, essays, fictional books, plays, poetry and musicals has written about.
He'd arrived early to a party at his friend's new flat and, because the host had not yet come home from work, the woman who rented the room to him let Leo in.
"I'm Karen," she said. "My boarder won't be long so we might as well have dinner together. Can you cook liver?"
While he fried the liver and she prepared the vegetables, they talked about music and art and writing. Karen was a singer and musician, and her mother was a well-known poet whose work had been banned in her native Germany because she was Jewish.
As a child, Leo, also Jewish, survived Nazi persecution by being hidden in safe houses. They talked deep into the night while the friend's room-warming passed next door.
"We were lucky from the very beginning," Karen said. Leo adds, "We have so much in common."
On April 2, the Cappels celebrate their 60th wedding anniversary. They have lived in Whangarei for years, their journey here via Amsterdam, Christchurch, Auckland and Kawau Island.
"We have had our second best life in Whangarei. The best was the 10 years we lived at Kawau on our boat," Karen says.
They will share their diamond wedding anniversary with friends and family. And, to mark a milestone, the Cappels will open their music-and-art-filled home to a series of house concerts.
Leo played saxophone in a jazz band when they first met and she had studied piano - mainly because her strict father insisted - although singing was her real passion. Leo is known for making old-style instruments and the couple play a variety of them. They describe their music style as ethnic and classical, from various countries. Some of it goes back 5000 years while some is improvised, modern, interpretive. Their house concerts will include unrehearsed readings from Leo's own musicals, accompanied by the music he wrote himself, and perhaps poetry read by themselves and guests.
Last year, the Cappels spent a month at South Pacific Studio, at Mt Bruce in Wairarapa, when Leo was invited to be writer-in-residence. They took instruments and performed for the local community. Recently they spent a similar time at Wharepuke in Kerikeri.
Their 60 married years have been happy. There was "a tough period" in 1965 when Leo's job making displays for museums took them and their two sons from Christchurch to Auckland. Leo had been involved with the arts and sculpture movement known as "the Group" in Christchurch and Karen sang in a choir. But, in Auckland a special museum project saw him work seven days a week for 13 weeks solid. This was before they had made new friends and again immersed themselves in the culture of art, music and literature. It was an awful time and shook their marriage.
"And we decided we will never let that happen to us again," Karen said.
They play a small tune for the photographer, Karen on an instrument modelled on an old Dutch ommel, while he plays something else resembling a zither, using a feather as a bow. It's 60 years of marriage, lived in tune with each other.
"With the two of us working together ... you can't go wrong," Leo says.