What happened was this. I found my way, not without difficulty, to the Barry Memo Arts Centre, got my ticket, had a chat with the librettist, stopped to order an interval drink, then turned round to discover that the entire audience had disappeared, as if eliminated by a Star Wars de-atomiser, or whatever those things are called. Two or three of us ran outside, looked this way and that, and after a few panic-stricken minutes tracked down the audience, who had gone right round the building in a crocodile and re-entered it by a door on the far side.

Seventy years ago, almost to the month, Welsh National Opera took to the stage for the first time with a double bill of the terrible twins, Cavalleria rusticana and Pagliacci; and fifty years later the company celebrated with the same two works directed by Elijah Moshinsky, designed by Michael Yeargan. To repeat the exercise in the same productions after another twenty years might seem an egregious piece of navel-gazing. But Moshinsky made a clever point with his 1996 staging, about stylistic distances travelled and technical standards raised.

War may be a dramatic affair for anyone involved in it, but staging it is another matter. In fact describing it satisfactorily at all needs either a Tolstoyan flair for the large canvas, or else a poetic genius for directing its force inwards, into self-reflection or religious contemplation or the kind of intense verbal music, rich in historical and literary allusion, that the great Welsh artist and writer David Jones made his own in his long, tragic prose-poem, In Parenthesis.

The third of Beaumarchais’s Figaro plays, La Mère coupable, is a very different affair from the other two, in that it records actual adultery and its disastrous consequences (including Cherubino’s death in battle), as opposed to the largely comic innuendos and mistaken identities of The Barber and The Marriage.

From the more or less inconsequential wit and bravura of The Barber of Seville to the profound comic psychology, social nuances and unparalleled musical genius of The Marriage of Figaro, and from the silly antics of Sam Brown’s Rossini to the style and brilliant stage management of Tobias Richter’s Mozart, is a good lesson in music theatrical history played backwards.

The latest themed season from WNO, to add to their fallen women, Donizetti queens and what not, goes by the slightly worrying title (for anyone with a short attention span) of “Figaro Forever”, and consists of an operatic sequence derived from Beaumarchais’ three Figaro plays and ending with a new opera by Elena Langer partly based on the last of them, La mère coupable.

How ironic that English National Opera turned out possibly the two best productions of the year after the Arts Council had done its grant-cutting worst, punishing the company simply, it seemed, for not being the irrationally preferred Royal Opera. And while 2015 has been as good as it gets artistically speaking for ENO, 2016 may well see confirmation of the first steps towards its dismantling by a short-sighted management – for what is a great opera house without a big chorus or a full roster of productions, both elements under threat?

Dickens’s public readings from his novels were almost as famous and popular as the novels themselves. He would write special scripts that gave prominence to particular characters and that dramatized the salient events of each story; and of all these performances, A Christmas Carol was one of the favourites, his and his audiences’. So what better idea than to turn this unforgettable tale into an opera: an opera for a single singer, dramatizing the story, impersonating all the main characters, being, as it were, Dickens himself with added music?

There’s a good deal to be said for semi-staged opera. It concentrates the mind in a particular way; it brings the orchestra more fully into the action; it moves the singers closer to the audience; and above all it reduces – even removes – the power of the director to superimpose some crackpot notion of his or her own on the dramaturgic design of the composer and librettist.

If nothing else, Stephen Sondheim’s best-known work will put you off pies; it will put you off barbers; and it may in the end put you off Sondheim. Popular though it seems to be with planners and programmers, it’s sluggish and heavy going as drama and thin gruel as music: three hours of clever musical patter, repetitive orchestral mechanisms, and slinky variations on the “Dies irae”. When you’ve seen one throat-slitting, one human pie-bake, you’ve seen them all.