A journey into dreams through songs from Dowland to The Kinks; a Swiss director who, Covent Garden’s Director of Opera Kasper Holten assures us, is “one of the most important European theatre artists”; a Norwegian chanteuse who, I assure you, is a performer of real originality. All that should add up to something just a little bit extraordinary, shouldn’t it? Sadly not. What I saw last night was the kind of thing I’d shrug off having chosen at random from offerings at the Edinburgh Fringe.

Composer Tansy Davies and librettist Nick Drake’s opera Between Worlds cannot help but be a devastating tribute to the tragedy of 9/11. Yet the whole is peppered with problems that mean this result is achieved only intermittently. Davies – whose first opera this is – and the playwright Drake, with Deborah Warner directing, have picked a topic that would seem at first glance to demand the scale of a modern-day Götterdämmerung. The result they extrapolate is far from that – but when it does succeed, it is in ways that are not really about 9/11 at all.

There was a moment half-way through Jonathan Dove’s children’s opera Swanhunter when I suddenly realised why pantomime developed its convention of the principal boy. Having a grown man prancing and posturing boyishly for the entertainment of a room full of kids feels odd, affected somehow, distorting the simplicity and sincerity of the tale being told. Which is a shame when, as here, the theatrical trappings are so vivid and enticing.

Still they keep coming, 35 years on from the London premiere of Sondheim's "musical thriller": Sweeneys above pubs, in pie shops, concert halls and theatres of all sizes, on the big screen, Sweeneys with symphony orchestras, two pianos or a handful of instruments wielded by the singers, Sweeneys as musicals and as operas, the dumpy and the tall. Which type was this one? Not a vintage English National Opera production, that much seems clear.

All Savoyards, whether conservative or liberal towards productions, have been grievously practised upon. They told us to expect the first professional London grappling with Gilbert and Sullivan’s eighth and, subject-wise, most problematic operetta in 20 years (23, if the reference is to Ken Russell’s unmitigated mess, one of English National Opera’s biggest disasters). Yet this is not Princess Ida as the pair would recognize it.

Johann Christian Bach’s Amadis de Gaule, which is receiving its first London run this week in a vivid and charming production at University College London Opera this week, suffered like many a talented work from the blinkered whims of musical fashion. History has generally focused on more pressing issues in late 18th-century Paris than the operatic rivalry between the schools of Gluck and Piccinni, but Bach’s failure to please either faction along with the minor disturbances of 1789 has, it’s believed, caused the subsequent neglect of this poignant and sensuous piece.

If you’re looking for rare festival Handel, better a pasticcio – take that as shorthand for a cut-and-paste job mostly from previous hits – than one of those original operas in which the composer only goes through the motions (and I’ve heard a few). Call in a reasonably cutting-edge director, make sure you have a motivator of the calibre of Laurence Cummings in the pit – not difficult in this instance, since he’s the devoted force behind the London Handel Festival – and find the brightest and best of young singers.

When is a famous aria more than just a showpiece? When it’s a narrative of a future event conjured by a hope beyond reason, which is what Madama Butterfly’s “Un bel dì” (“One fine day”) ought to be but so rarely is: too often prima donna overkill and stereotyped mannerisms get in the way. Not with Latvian soprano Kristine Opolais. Her Butterfly’s gestures can be stylised but always unusual, setting her apart, an ex-dancing geisha driven almost mad in a three-year wait for a “husband” who won’t come back. The effort of will sees her crumple in the aftermath of her vision.

“Do you think they’ve got enough plot to get us through to the end?” I overheard a lady anxiously asking her husband during the interval. It was a fair question. Donizetti’s The Wild Man of the West Indies was written within a year of L’elisir d’amore, and the two operas share many things, but not that spark of genius that can transform a pantomime into a drama. Rarely has so little happened in an opera, and with even less effect.

"No heckling. No smoking. No making love," read the nifty video projections announcing the rise of the new Mahagonny at the Royal Opera House. Why so coy? Could they not give us a bang for our buck, or even a slow comfortable screw?