To Charles Rosen it was a work of "rarely redeemed dullness". The wife of Emperor Leopold called it "German rubbish". It's pretty obvious why so many have objected to Mozart's final opera La clemenza di Tito. Tunes (memorable ones) are by and large lacking, which is odd for Mozart. The overture is not something you'd want to hear on its own. And the work's great solo arias are unwieldy in form (though fascinatingly so) and tricky to sing and separated by the vast wastes of a notorious recitative.

Such a pity about Beatrice and Benedict! As a musical visualiser, a creator of musical tableaux, a radio composer avant la lettre, Berlioz had few equals. The Damnation of Faust is surely the greatest radio opera ever written. But for some reason he had no grasp of the stage. Benvenuto Cellini is a lifeless succession of spectacular tableaux. The Trojans must have more superb music per square yard of ineffective drama than any work of comparable length.

When blithe Susanna and not the expected Cherubino emerges from hiding before the astonished Countess and enraged Count, the latter instantly back-pedals on the fury he has been heaping upon his seemingly faithless wife. She rounds on him: “Crudele, più quella non sono!” (“Traitor, I am no longer her”) and everything suddenly stops. It's a tiny two-beat rest that usually goes for nothing except the signal for a key change, but here the moment is charged with drama. The Count shoots apologetic looks to cover his shame and the Countess painfully registers her lost trust.

Famously, at its Venice premiere in 1853, La traviata had trouble with the censor, not only over the salty innuendos of the plot, but over the simple fact that it was set in the present day and in contemporary costume. A rule like that would finish off most updated modern stagings (and no bad thing at that). But David McVicar’s now two-year-old staging of Verdi’s early verismo masterpiece in Cardiff's Wales Millennium Centre wouldn’t be one of them.

For all its comic fantasy and lilting tunes, there’s nothing pastel-coloured about Offenbach’s The Tales of Hoffmann. Deaths are frequent and bloody, humour is macabre, and emotions run high – being late to the pub is cause enough for violence and conspiracy theories. It’s a world of sliding screens, where a smile always threatens to become a leer, a kiss a murder. Who better (who else?) to inhabit this operatic fantasy-land than Richard Jones, a director who relishes the elision and collision of kitsch and the grotesque.

As in sex, so it is in music: there’s a lot riding on the climax. The celebrated third act trio of Der Rosenkavalier is arguably the most famous orgasm in music – dear reader, can you name a better one? – but time it wrongly and you’ll regret it. There is, however, absolutely nothing regrettable about this A-list cast in the hands of director David McVicar and conductor Edward Gardner. Theirs is the most assured, most riveting Rosenkavalier in this country for years.

Francesca Zambello’s production of Don Giovanni may only be 10 years old, but is already showing signs of decrepitude. Even back in its youth in 2002-3, this staging never had much of a spring in its step, but at least there were some fantastic casts to compensate. Bryn Terfel, Anna Netrebko, Simon Keenlyside and Erwin Schrott have all taken their turn here, but even with Gerald Finley returning in the title role there’s little the current incumbents can do to do rescue this aged and confused attempt at a seduction.

It’s the pace that takes getting used to in a Baroque opera. Five words in the libretto can easily take up five minutes to sing, and Handel’s music is often disconcertingly jaunty, even when tragic events are unfolding. Tim Albery has also directed Opera North’s current Madam Butterfly revival, a thrillingly cinematic, fast-moving production. His Giulio Cesare is judiciously pruned, with a total running time of about three hours. The cuts prevent any sense of stasis; what’s remarkable is just how much entertainment Handel’s imperial epic provides.

Two precisely imagined dream-visions bookend a cornucopia on the musical front. I’ll start with the deadly but save the apparently frivolous for the top slot. Christopher Alden’s pitiless exiling of Britten’s A Midsummer Night’s Dream from Elizabethan wood to 1960s school block was to opera what Lars von Trier’s Melancholia was to film: audience-sundering, often alienating, sometimes enticing, but very much its own consistent world. Its splendid cast and conductor Leo Hussain worked as one to enhance the paradoxes of its terrible beauty.

The Barbican has always led the way in London in international theatre programming. The year there ended on a high, with Thomas Ostermeier’s Hamlet from the Schaubühne laying down new markers for transgressive commitment. I was sceptical about it when I saw the Berlin première in 2008, and our own critic was not, commendably enough, in a mood to be fooled around with. Yet a production which stages, so stylistically, terror, insanity and loathing (all in Shakespeare) with six actors straining every sinew without entirely ridiculing the play has to be respected.