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.

It’s almost impossible to imagine what a Handel opera performance can have been like in London in the 1730s, when Orlando first appeared. The audience came primarily to hear their favourite singers: and these must have been sensational, if not unduly dedicated to the dramatic verities they were supposed to be representing: castrati like Senesino and Farinelli, sopranos like Cuzzoni and Faustina (who once came to blows onstage, presumably trying to upstage one another).

Whatever one may feel about Bellini’s music, it’s hard to think of him as in any sense a political composer. So you could almost hear the hearts hit the floor when the curtain went up – or rather was as usual already up – on the opening of Bellini’s Puritani with Orangemen and a scruffy Catholic Arturo instead of good old Roundheads and Cavaliers. Surely Annilese Miskimmon isn’t trying to make Bellini relevant and meaningful, with Elvira’s madness as some kind of reductio ad absurdum of power-sharing.

September is upon us and it’s nearly time for the new season. English National Opera’s Artistic Director John Berry may have left the building but his enterprising legacy lives on in a 2015-16 season that looks on paper as good as any in the past 20 years; what happens after that is anyone's guess. Still, there shouldn’t be too much grief that ENO Music Director Edward Gardner has moved on, since his successor Mark Wigglesworth already has a fine track record with the company.

Debussy completed only one opera (though he started plenty), but it’s the most perfect work imaginable, not only in sheer musical refinement and narrative precision, but in psychological penetration and above all in that exact grasp of the irrational nature of the medium that distinguishes the greatest operas from the merely effective.

I must have been one of the few in Saturday’s audience for Richard Ayres’s new opera who had never seen Barrie’s play or read the book, so I’m unable to judge how faithfully it renders the original – in case that matters. Somehow one knows the dramatis personae: Peter Pan himself, the Darling family, Nana the dog-nurse, Captain Hook, Tinkerbell, Tiger Lily and of course the ticking crocodile, who swallowed Hook’s watch along with his arm. They are all here, wittily, sometimes brilliantly, reimagined in Keith Warner’s panto-like staging.

There’s a lot to be said for concert performances of Wagner. Not only are you spared the post-prandial lucubrations of aspirant directors – the moonmen and the fighter pilots, the jackboots and the biogas installations. But it’s possible to concentrate on Wagner’s greatest theatrical gift: not his stagecraft or stage imagery, but his management of time and psychological growth through purely musical means.

After 16 years one might expect a revival of a repertory opera like Hansel and Gretel to come up with a dusty look and frayed edges. But Benjamin Davis has done a brilliant job pumping the life back into Richard Jones’s memorable but intricate 1998 staging of Humperdinck’s pocket Wagnerian masterpiece.

So easily parcelled up as a master of opera buffa, Rossini is a composer who constantly surprises by the emotional and intellectual range of his best work. William Tell, which opened WNO’s current season three weeks ago, is a major progenitor of Verdi, even arguably Wagner: grand opera devoid of what Wagner himself called effects without causes.

Popularity is all very well, but it can be a poisoned chalice. Braving the umpteenth revival of Carmen at WNO (original directors Patrice Caurier and Moshe Leiser, revival director Caroline Chaney), I began to experience that sense of weariness that sometimes afflicts the dutiful end of the repertoire: Bizet’s masterpiece along with the relentless Butterflies and Toscas, the Figaros and Barbers. That feeling that the work and its myriad devotees will somehow get us through in the absence of anything resembling artistic necessity.