Anna Magdalena led a strenuous and stressful life. A gifted singer and musician, she married an egotistical and obstinate genius who believed the world should revolve around him, and complained when it didn’t; she worked constantly and loyally to advance the family’s business, which was music; she was pregnant every year from 1723 to 1737, bearing 13 children, seven of whom died in youth.

After her husband’s death, she becomes only “the widow Bach” in contemporary documents — bound, as bad luck would have it, for a pauper’s grave and forgotten except by a few scholars of baroque music and others with an obsessive interest in her husband. Her husband, Johann Sebastian Bach, never died. The “father of all harmony,” as Beethoven called him, lives on in immortality.

A new documentary is now attempting to lift her — and by implication, women of the past whose musical accomplishments have been “hidden from history” — from obscurity.

In “Written by Mrs Bach,” about to premiere in London and then move to Germany, a professor of music, a composer and an American expert in document forensics advance the case that Anna Magdalena Bach actually composed some of the most notable works attributed to her husband, Johann Sebastian Bach.

The works in question are immortal masterpieces:

“Written by Mrs Bach” relies on the work of three people: Martin Jarvis, a Welsh-born conductor, musician and professor of music at Charles Darwin University in Australia; Sally Beamish, a British composer; and Heidi Harralson, an Arizona-based expert in document forensics.

They don’t prove their case and don’t purport to. “There’s circumstantial evidence,” Jarvis said in an interview with The Washington Post. “Plus there’s strong musical evidence.” It’s a theory — and it’s plausible.

The argument rests on three legs: The pieces, according to the researchers, deviate from other Bach works in significant structural and technical respects; the manuscripts appear to be in the hand of Anna Magdalena with one front page actually saying “written by Mrs Bach” in French; and there is no proof Bach actually composed the works, only the possibly groundless assumption the composer wrote everything attributed to him. He left behind few personal papers, which might aid in documenting his work.

“When I was told about the theory about Anna,” Beamish said in an interview with The Washington Post, “I thought, ‘That’s impossible. She couldn’t have done it.’ Then I thought, ‘What am I saying?’ I’m a full-time professional composer. I wanted to look at the reasons why it was thought women couldn’t compose through the centuries.”

Jarvis developed suspicions about Bach’s authorship when, as a young student at the Royal Academy of Music in London, he first played the cello suites. “This was when I became really concerned that this particular music was not written by Bach,” he said in a 2012 lecture, “at least as far as I knew his music — and this was the beginning of my journey of 34 years to find the true composer of the cello suites.”

Jarvis acknowledged his theories made him a pariah among some music historians — by the “Bach scholarly world,” as he put it, which for the most part has greeted his theory with skepticism at best.

But his argument is seductive. Anna Magdalena was a gifted singer from a family of musicians, which is apparently how Bach came to meet her when she was a teenager. The couple married in 1721 after the death of his first wife.

Bach was employed as a court musician and then “Kapellmeister” — essentially, a music director and teacher — for German princes, churches and towns, most notably Weimar, Cöthen and Leipzig. His job required the regular, even weekly production and performance of religious works as well as composition on-demand from bigwigs for special occasions, which helps explain why Bach was so prolific. He had to produce. The catalog of confirmed fugues, sonatas, cantatas, masses, concertos, sinfonias, inventions and more numbers more than 1,100, and other works were probably lost.

Keeping up with demand required a family business — a “workshop industry,” said composer Beamish: “As a family you’ve got to keep things together. We know that his sons had a hand in pieces of his. But why not her?” Said Jarvis: “There’s an overwhelming sense of team composing.”

Indeed, Bach offered his family as a package. “All are born musicians and I can assure you that I can already form an ensemble” of vocalists and instrumentalists “within my family, particularly since my present wife sings a good, clear soprano, and my eldest daughter, too, joins in not badly,” he wrote in 1730 to a prospective employer. She was regarded highly enough, Jarvis said, that she was paid — and paid well — for her services by Prince Leopold of Cöthen.

She certainly knew how to write music. She was among the many copyists who scrupulously reproduced Bach’s scores for distribution, which is why it wouldn’t be unusual to find his pieces in her handwriting. But, said Jarvis, Beamish and Harralson, the American document forensic expert, it would be unusual to find editing of a manuscript in Anna’s hand on a score meant to be an exact copy.

But that is indeed what they found, she said in an interview. If “you’re a scribe and copying a manuscript, you’re going to make sure there are no mistakes,” she said. The manuscripts she examined in Anna’s hand did not look “copied from another source. … It looks like an original manuscript and somebody’s been making edits to it.” And that somebody is likely Anna.

To say Bach’s wife wrote some of the works attributed to her husband does not diminish his work, said Jarvis, “not a jot.” Nor is it the first great work attributed to Bach and then questioned, the other being the thunderous “Tocatta and Fugue in D Minor” for organ.

So little was known about the composer’s life that his death left a vaccum, which would be filled by others in the decades after his death in 1760.

Bach, said Jarvis, is “a construct of the mid-19th century. … Germany needed a cultural hero and Bach became it.”