The singer first met Bach at an EMI record label bash in 1985, although their relationship remained platonic for more than a year before they started dating.
Despite the age difference, the pair have enjoyed a blissfully happy romance, something she referred to during a 2006 interview with talk show host Oprah Winfrey, in which she shot down any notion of marriage.
People often ask me why don’t I marry,’ she said. ‘I have love. I have a good life. I don’t need to interfere with that. For some people, marriage means “You’re mine now.” That can be the beginning of the failure of a relationship.’
She added: ‘Psychologically, something happens when someone says, “You’re my husband or wife. You can’t do this or that.” It’s about ownership. That freedom that two people loving each other and wanting to be together – and being able to leave if anything is wrong – is gone.
‘Neither Erwin nor I feel the need to get married. We’ve been together for 18 years. What would marriage give me that I don’t already have? Marriage would be about pleasing the public. Why do I need to please the public if I’m already pleased?’
The singer has two children, sons Craig, from a relationship with late saxophonist Raymond Hill in 1958 and Ronald – her only child with Ike.