It’s often said that Ariadne auf Naxos is all about The Composer – not only Richard Strauss but an affectionate parody of his younger self – and Katharina Thoma takes this idea seriously in her Glyndebourne production.

Why stage a stiff opera about half-frozen royals by a not-yet-divine Mozartino? The best Mitridate really deserves is one of those intimate concert performances with brilliant young singers at which Ian Page's Classical Opera excels.

Perfect comedies for the country-house opera scene? Mozart's Figaro and Così, Strauss's Ariadne - and Britten's Albert Herring, now 70 years and a few days old, but as ageless as the rest. With the passing of time it's ever more obvious that this satire of provincial East Anglian tricks and manners also has universal appeal and stands with the best.

Opera directors must, I suppose, direct. But one could wish that they kept their mouths shut, at least outside the rehearsal studio. The condescension in Longborough’s programme-book interview with the director (Orpha Phelan) and designer (Madeleine Boyd) of the festival’s new Fidelio beggars belief.

Recorded on disc, this cast would be extraordinary for much of the time — to look at, not so much.

A drama of passion for essentially passive characters, Debussy’s one and only completed opera is a masterpiece of paradox. How do you stage a work whose dramatis personae hardly seem aware of their own destructive feelings, and who inhabit their island world like the blind who, according to Pelléas, used to visit the curative fountain but stopped doing so when the king himself went blind?

Der Rosenkavalier, you might think, is one of those operas that belong in a specific place and time and no other. “In Vienna,” says Strauss's score, “in the first years of Maria Theresia’s reign” (i.e. the 1740s). But this, of course, is a provocation.

Nature’s germens tumble all together rather readily in more recent operatic Shakespeare. Following the overblown storm before the storm of Reimann’s Lear and the premature angst of Ryan Wigglesworth’s The Winter’s Tale, what's rotten in the state of Denmark rushes to the surface a little too quickly in Brett Dean's bold new take on the most challenging of all the tragedies.

It’s all there in the first few bars of Britten’s music – that unsettling tension between beauty and familiarity, and eerie, undefinable otherness. Those cello glissandi might end in glowing major chords, but the tentacle-like slides throw them into doubt. We’re no longer in a binary world of major or minor, but a harmonic landscape of infinite possibility.

The Longborough Festival was started, essentially, to perform Wagner, and Wagner is still what it does best. This revival of Carmen Jakobi’s production of Tristan und Isolde is the strongest argument imaginable for small-theatre Wagner.