Not that men are excluded from the annual three-concert series: they are allowed to have their music performed, just as they are allowed to play in the orchestra. But Tuesday's concert is typical, in that there's a female connection to each work on the programme.
Mozart wrote his Piano Concerto in G (K453) for a gifted pupil, Barbara von Ployer. His Divertimento in B flat (K287) - whose busy violin part will keep the Ambache CO's leader, Sophie Langdon, thoroughly occupied - was composed for the name-day of Countess Lodron, the sister of Mozart's hated employer in Salzburg, Archbishop Colloredo (the music sounds as if Mozart liked her rather better). Also on the bill are the Concerto for string orchestra of 1948 by the Polish composer Grazyna Bacewicz, and the Piano Concerto in B flat by Nanette von Schaden. (Nanette von who? More of her in a moment.)
Ambache didn't start out with the intention of mounting a crusade on behalf of women composers. It's simply that, as she explains, someone had to do something about a genre of cultural censorship that for centuries allowed women to do certain things in public - sing, play and dance, for example - but not others. As Clara Schumann once wrote, "A woman must not desire to compose - not one has been able to do it, so why should I expect to?" And if a musician of her legendary talent felt browbeaten into effective self-censorship, what chance can other women composers have had?
Ambache came to ponder these questions by an indirect route. "It's really my love of Mozart that started it all off," she says. "I began to play his concertos while I was a student at Sheffield, and I always liked directing them from the piano, which was how Mozart used to do them. Then, after I'd graduated and I wanted to do this professionally, I realised that the only real way of making it happen was to have my own orchestra. It looked as if the last thing London needed was yet another orchestra, but we did have an agenda that was a bit different."
The Ambache Chamber Orchestra gave its first concert in 1984, and has since evolved into a regular presence on the scene, slimming down to the Ambache Chamber Ensemble as and when required by its choice of repertory. In this, the music of women composers soon began to feature. "Mozart's concertos were central to our concerts from the start, and they'll continue to be," says Ambache. "But I was looking for different things to do as well. And it wasn't like coming across the occasional, isolated work by a woman composer - I was amazed at the quantity of music that's been composed by women."
So why do we seem to hear so little of it? "This goes back a long way. In Mozart's day, there were women who were famous and successful musicians. He wrote many of his piano concertos to play himself, but all the others - without exception - were written for woman pianists, and the music shows just how good they were. But becoming known as a composer was different. In that department, women faced a brick wall.
"Take Clara Schumann. She seems to have ended up doubting whether she had any talent for composing at all. We gave the British premiere of her Konzertsatz for piano and orchestra, which is a really beautiful piece. And there must have been many situations like Fanny Mendelssohn's. She and her brother Felix came from a cultured and intelligent family which was obviously proud of her gifts as a pianist. But when she started showing a real talent for composing, the family just said, `You are not to do this - you're to get married instead.' So she did. And while she did go on composing, it was a long time before she had any of it published."
One woman musician whose posthumous reputation has risked disappearing even further towards oblivion is Nanette von Schaden. Her Piano Concerto in B flat receives its British premiere, an estimated 211 years after its creation, in Tuesday's concert.
Von Schaden's name will probably have been spotted in these islands only by compulsive readers of the footnotes to Mozart's collected letters. Here we learn that she was born illegitimate in Upper Austria in 1763, and at 16 was married to Joseph Wilhelm von Schaden - a privy councillor at the court of the Prince of Ottingen-Wallerstein, and the recipient of Beethoven's earliest extant letter (in 1787).
During an Arts Council-funded visit to the Deutsche Staatsbibliothek in Berlin, Ambache made the kind of discovery that every musical detective dreams of. "I suppose I'm quite a thorough researcher," she says. "But I can't say I was looking for anything about Nanette von Schaden in particular. Usually it's a case of turning up with a pile of card-indexes and just seeing what's there." What was there was a complete set of parts for Von Schaden's Piano Concerto.
Ambache's claim that this is a fresh and attractive work of genuine quality ties in with contemporary references to Von Schaden herself. After being officially adopted by her unofficial father and placed in a music-loving Viennese household, the young Nanette developed what was evidently a wondrous musical talent. One visitor to Ottingen-Wallerstein praised her "unsurpassed virtuosity" at the keyboard, adding that "she also sings with great expression and presence and is in every respect an agreeable and interesting woman". It is possible, if not certain, that she met Mozart in Vienna, and probable that she knew Beethoven, to judge from his correspondence with her husband.
Yet both she and her music seem to have been utterly forgotten after her death in 1834. She is known to have composed another concerto, but no evidence of other works has come to light. It's just one more instance of the kind of injustice with which Ambache feels women composers have always had to contend. "It's a more complex situation than straightforward prejudice. Sometimes these things go in cycles. Fanny Mendelssohn was forgotten for a while after her death, but around the turn of the century there were a number of performances of her music. Then it went out of favour again, and now it's being rediscovered once more.
"But the same problems are always there. Look at this year's Proms. There isn't a single work by a woman in all 72 concerts. Not even in Clara Schumann's centenary year. Sometimes you wonder how much anything changes."
The Ambache Chamber Orchestra's `Mozart & Women of Note' concert is at 7.45pm on Tuesday, QEH (RFH2), SBC, London SE1 (0171-960 4242)