In 1840, precariously lodged in a hôtel garni in Paris, and unable to service his extravagant tastes in decor, drink, food and fashion, Richard Wagner, the composer who would change harmony forever with one chord, was forced to make ends meet by preparing arrangements of operas by other, more popular composers: Auber, Meyerbeer, Bellini and Donizetti. The bruising, tantric beauty of Tristan und Isolde and the unanswerable question posed by its signature chord of F, B, D sharp and G sharp would have to wait for nearly twenty years to be realised on the page. In the meantime, he applied himself to preparing a vocal score of L’elisir d’amore.

Some people have a gift for turning tragedy into comedy. Others turn comedy into tragedy. There are few belly laughs in Wagner’s prolix 1868 romantic comedy, Die Meistersinger von Nürnberg, which ends with Eva running off to what will surely become a miserable marriage with an experimental composer whose music is too sophisticated for the common ear, instead of marrying a man who not only understands her but makes shoes for her pretty feet.

By contrast, L’elisir d’amore, Donizetti’s 1838 reworking of Auber’s earlier romance, Le Philtre, is one of a very few operas to be equally funny, touching and useful. The main musical joke, a ‘barcarolle’ sung in 2/4 time (‘Io son ricco e tu sei bella’), is less laboured than poor Beckmesser’s humiliation in the Nuremberg song contest. You don’t need to know that barcarolles traditionally lilt in 6/8 time to enjoy the wit of Felice Romani’s flirty libretto.

Drinking one thing while believing it to be another is the link between L’elisir d’amore and Tristan und Isolde, the legend of which Adina is reading aloud to her workforce at the start of the opera. Desperately in love with Adina, Nemorino longs to get his hand on a similar love potion. Enter Doctor Dulcamara, the encyclopaedic snake-oil salesman, with an elixir that promises relief from apoplexy, asthma, hysteria, wrinkles, tinnitus, paralysis, erectile dysfunction, indigestion, halitosis, mice, bedbugs, balding and broken hearts.

Where Isolde swigs her love potion by accident, intending to drink poison, Nemorino takes a guileless glug of cheap red plonk that is disguised as a cure-all, setting in motion a series of events that makes Adina realise that love was right under her attractive nose all along, shedding the famous tear observed by Nemorino in ‘Una furtiva lagrima’. The moral of the story, purring along beneath a succession of deliciously catchy tunes and witty orchestral details, is that a little of what you fancy does you good.

No one drinks themselves to oblivion (like Hoffmann in Les Contes d’Hoffmann) or disgrace (like Cassio in Otello) or local notoriety (like the virginal hero of Albert Herring) in L’elisir d’amore. Although Dulcamara’s elixir is sold as a drug it is not as addictive as the laudanum on which the pub-averse busybody Mrs Sedley is dependent in Peter Grimes. Search the canon for further useful life lessons, however, and you’re more likely to learn by negative than positive example.

Dating outside of one’s age group (Don Pasquale) and body type (Falstaff) is firmly discouraged, as is falling in love with a man or woman with a past (La fanciulla del West and La traviata). Assuming those hurdles to heteronormative happiness have been jumped, and a family has been started, opera provides a catalogue of bad parenting from and of both sexes. The backstory of Il Trovatore is an extreme example yet even in the abject misery of Wozzeck a shred of decent advice persists: we should all eat our beans and pulses. As to Gianni Schicchi, the moral is clear: never cheat a cheater.

The most satisfying comedy is one that is executed with equal acuity and tenderness – one that fully exposes the faults of a personality, or group of personalities, and acknowledges that we are none of us immune to those faults. Are Buoso Donati’s greedy family really so frightful? Only in respect of their snobbery towards Lauretta, whose engagement to Rinuccio Schicchi secures through his trickery, earning our forgiveness if not that of 13th-century Italy.

Forgiveness is key to the happy ending from the balm of Countess Almaviva’s response to her husband’s apology at the end of The Marriage of Figaro to the soothing anthem that the animals sing to the chastened child at the close of L’enfant et les sortilèges. That the Count will stray and the child will dawdle over his homework again is not the point. For a few minutes, all is held in a perfect embrace of harmony.

Though WH Auden and Chester Kallman’s libretto for The Rake’s Progress is often accused of being arch and cold, neither of which it seems to me, the final ensemble, with Tom, Anne, Baba, Nick Shadow and Trulove on stage, sans beard and wigs, rings true: ‘For idle hands/And hearts and minds/The Devil finds/A work to do’. Even quite clever people do very silly things, on stage and in real life, especially when we have the leisure in which to indulge our worst selves. And what could be more indulgent than lamenting lost love on a deserted island and listening to one’s own words echoed back?

It’s a measure of Strauss and Hofmannsthal’s genius that the balance of comedy and tragedy is so exquisite in Ariadne auf Naxos. In the backstage Prologue we have already been exposed to the Prima Donna as herself: neurotic, petty, egotistical. In the Opera proper, she becomes Ariadne, a tragic figure made ridiculous by heartbreak. Instead of chardonnay, like Bridget Jones, she is drunk on the voluptuous sorrow of her own arias ‘Ein Schönes war’ and ‘Es gibt ein Reich’ and quite immune to the good sense imparted by Harlequin in ‘Lieben, Hassen, Hoffen, Zagen’.

Even Zerbinetta’s coloratura address ‘Grossmächtige Prinzessin’ fails to shift Ariadne’s mood. Zerbinetta’s point is that there are plenty more fish in the Aegean sea. Only when one of them turns up in the form of Bacchus, another duped soul on the rebound, does Ariadne learn that lesson. That their music is beautiful enough for us to look past their faults, to set aside the double layer of theatrical conceit and the shabby backstage behaviour, and to reflect on our own experience is where the magic lies. As Zerbinetta observes, ‘Kommt der neue Gott gegangen, Hingegeben sin wir Stumm!’ Love, like wine, good fortune, or the perfect embrace of music, mightn’t last forever, but a little of what you fancy does you good.