Erika Fox’s coffee mug is emblazoned with the title of HG Wells’s The Invisible Man. One can’t help noticing, because this extraordinary composer has for too long been an almost invisible woman. Today, her first-ever commercial CD is released, featuring a selection of her chamber music. She is 82.

Musical cognoscenti reacted with horrified astonishment to the realisation that Fox’s music has not previously been recorded. Its style is tough yet mesmerising, highly individual, with a strong undertow of unsettling emotion. “Some people have said it’s challenging, but because it’s mine, I don’t think of it that way,” Fox remarks. “To me it’s ordinary. It’s what I do.”

She lives in west London in a house overflowing with books and music, her home on and off for decades. Her music is much like her upfront personality — warm, perceptive and forthright, with a refreshing dislike of “pussyfooting around”. But it has also been nurtured with many difficult and painful memories.

Being born into a Chasidic family in Vienna in 1936 would be a fearsome start in life for anybody. “My grandfather on my mother’s side was a well-known rabbi, Shalom Hager, from Stroznic, Romania,” she says, “who moved to Vienna and had a stiebel.

“In this house a lot of us lived together, which was more common then than now.

“When Hitler came in, life for Jewish people there was almost at an end. Some of us were very lucky indeed. My father, also from a rabbinical family, was the black sheep. He was the only one who spoke good German — otherwise, everybody spoke Yiddish —and he managed to get false papers for some people.”

The toddler Erika and her mother were the last to leave. “My father left much earlier. I didn’t see him again until I was 12 because he did not come to Britain, but went by ship to Palestine and joined the British army. I was actually not on my mother’s passport and it’s a miracle that I am here at all.” People then, she says, were not as hostile to immigrants as they are today; she suggests that authorities turned a blind eye.

After a spell in a home for Jewish refugees in the East End, Fox’s family moved to Swiss Cottage and there set up another stiebel. “The area was chockablock with refugees. Our house was called Beit Shalom after my grandfather. I was allowed in the men’s section as a little girl because I was very close to him. He adored me, and he taught me to read Yiddish at the age of three, long before I ever read English. And the first music I ever heard was his prayers in the synagogue. “Many things stayed with me; for instance Simchat Torah with a lot of dancing and singing. That early listening went into my music; those tunes were part of my life and still are.”

Echoes of Chasidic music and rituals permeate her compositions to this day.

Still, there was horror to absorb as well as rapture. “One of my childhood memories,” she says, “is that we would come down on a Sunday morning, put the wireless on and listen to Hitler. His speeches were broadcast and I still remember them because he always shouted. He was screaming his head off and once he said ‘Ich werde eure Städten ausradiern’ — ‘I will rub out your cities’. And I thought: gosh, he must have a huge rubber! Small children don’t say anything, so I never told a soul, but I was terrified of this man with his huge rubber…”

During the Blitz, Fox and her mother were evacuated to Yorkshire. In a cavernous, sparsely occupied refugee home in Leeds, the child Erika encountered a piano. “The door to the living room was locked but there was a hatch that would have been used for serving food. I got a chair and climbed through it every day to ‘play’ the piano and make up tunes. That was the beginning.”

Back in London, her mother took some friends’ advice and sent her to play to the head of the Royal College of Music’s junior section, who helped to find her a teacher: the harpsichordist Millicent Silver, who gave her free lessons and took her to hear Myra Hess play at the National Gallery.

But as she grew up, it became clear that music was not accepted as a suitable profession for a woman. “It was not seen that it was an important part of my life. It was not even remotely understood. I was meant to get married and have children and make cakes.”

She refused an arranged marriage, wed a chemist and had a son and a daughter. But one day she went to a concert at the Victoria and Albert Museum and bumped into Michael Graubart, head of composition at Morley College, who asked her what she was doing now. “I started crying,” she says. “I suddenly realised how unhappy I was. I was living someone else’s life, somehow. It felt as though I wasn’t here for any purpose at all.”

Graubart suggested she take lessons at Morley with Jeremy Dale Roberts, who became her mentor. “This man was entirely responsible for changing my life. He was an extraordinary musician and a very fine composer.” With his support, she began to find herself in earnest.

“That was, I suppose, the beginning of both my better life, but also my worse life when it came to my marriage, which really was not a good one after that,” she says. “My husband never accepted that I did other things. Many people who don’t do creative work don’t realise the work that has to go into it. They expect that if you’re inspired, it just trots out by itself.” Emphatically, it does not.

It is clear that Fox feels an absolute need to write music; she literally could not do without it. Yet between raising after her children and caring for her ailing mother, who was crippled by rheumatoid arthritis, and for her husband, who had Alzheimer’s for ten years, she struggled for decades to find the time.

“Lack of time focuses your mind on what you can’t live without,” she remarks. “I went sometimes to the Rural Music Schools Association, where you could book a room with a piano and work. Once I wrote an orchestral piece there in three days. I remember Jeremy saying: ‘I don’t know how you did that’.”

A stronger era in the 1970s-80s, when she was involved with leading new music ensembles and was often performed, seemed to go cold in the 1990s, not least due to these pressures— but she thinks other factors came into play. She is aware of the “unEnglishness” of her style, influenced by serialism and modernism besides the rituals and prayers of her Chasidic background: “The intensity of some new music of the time was rather rejected in this country; it’s very much a mainland European thing. Somehow I didn’t seem ever to fit in to the zeitgeist.”

Reviews of her music were positive and the composer Sir Harrison Birtwistle was among the peers who provided encouragement— “He once told me, ‘Everybody’s is the same except yours, which is different’. That was a huge compliment coming from him.” Despite all this, Fox says she continually found opportunities falling through. Staying positive must have been extremely difficult.

Once, the director of the Leamington Festival phoned her to commission a piece: “It came at a point when my husband was already very ill and I was terribly depressed,” she says. “I told him he had literally saved my life.”

She has no doubt, nonetheless, that she was affected by prejudice against works by female composers. In today’s explosion of consciousness about this deep-seated neglect, she has been a beneficiary. The composer Nicola LeFanu featured her in a 2016 broadcast on inspiring women in music on BBC Radio 3 and drew her to the attention of producer and broadcaster Kate Romano, who masterminded the new recording and has helped to set Fox up for life as a 21st century composer, with website, publisher, financial grant applications and more.

But Fox maintains clear-eyed scepticism. “There’s been a change in attitude towards women composers but I worry because I don’t know how deep it goes,” she says. “Things have always been difficult for women, just as things have always been difficult for Jews. If you’re Jewish, whatever you do you’re Jewish first. Likewise, you’re a woman first, and if you’re prime minister they tell you how you’re dressed…

“There are plenty of lousy, boring women composers. There are just as many lousy, boring men composers, but that will not be noticed. What will be noticed is, ‘Well, why haven’t you got a Mozart?’ So I do worry. So-called ‘progress’ doesn’t go in a straight line.

“But I’m not grumbling — I’ve got a CD out and that’s jolly good! I’m very glad that women are being allowed to be human. It makes a nice change.”

‘Erika Fox: Paths’ is out on 28 June on NMC Records