Each to their own!

"They all do it this way" – which is to say, women do! Let us be clear: the title of one of the most beautiful works in operatic literature, Mozart's Così fan tutté (1790), reflects a mildly sexist attitude. However, however marginally politically incorrect the expression, the congenial librettist Lorenzo da Ponte knew full well that this title was more exciting and curiosity-provoking than, shall we say, L'infedeltà delusa ("Deceit Outwitted", the 1773 comic opera from Eszterháza by Mozart's older contemporary, Haydn.) In the 19^th century "Così" was misunderstood; it was regarded as frivolous and immoral, although Mozart's gorgeous music expresses a deep truth: that our feelings are stronger than the moral ideas which have been thrust upon us. Or, as Woody Allen might say, sex is a dirty thing but only if you are doing it right...

Mozart was the first composer to malleably reproduce sexual desires and emotional seduction in music. The prancing yet uncontrollable adolescent Cherubino in the Marriage of Figaro (1786) ("Non sò più cosa son, cosa faccio") finds consummation in the conquests of the title character of Don Giovanni (1787) ("Là ci darem la mano"). But there was to be a successor to Don Juan's "genius sensuality" (Kierkegaard) in the guise of Bizet's hard-boiled figure of Carmen (1875).

The genre of opera first struck the notes of eroticism shortly after its inception. In the closing duet of The Coronation of Poppea (1642) Monteverdi creates the veritable prototype for a love duet; Wagner also employed its basic devices: the intertwining melodic lines and the repeatedly delayed melodic and harmonic resolutions are found in the ecstatic nocturnal encounter between Tristan and Isolde (1865). (Incidentally, the deceived husband King Marke and his entourage's arrival is an infinitely tragic instance of coitus interruptus.)

Nero and Poppea's consummated love – which is not immoral because of this – does not appear to confirm the warning which the spirits bestow on Alberich in Wagner's Rheingold (1869): "Only he who forswears love's power, only he who forfeits love's delights, only he can attain the magic to fashion the gold into a ring." Quite the opposite. In his sexual dependency on Poppea, Nero flattens everyone and every political obstacle in his path, a case of "winner takes all" – both power and a good woman! You bet it does! (And if we are talking about Alberich the dwarf: the psychological approaches of the early 20^th century led to unfulfilled amorous fulfilment, the sexual oppression of the "ugly" person – the anti-hero – becoming an operatic theme: Schreker's The Candidates (1918), Zemlinsky's The Dwarf (1922), etc.)

Can we call Poppea the first whore in the operatic literature? I fear that because of her limitless desire for power, her lack of moral inhibitions – at least in the metaphorical sense – the answer is yes. In Venice in 1659 a true courtesan by the name of Lucietta Gamba sang the title role of Elena by Monteverdi's pupil Francesco Cavalli, with – what's more – the "sponsored" support of one of the patricians of the city state, who was as keen on the female sex as he was on opera. "Quella putta che canta" ("what a singing whore") wrote the great librettist of the day, Gian Francesco Busenello, in one of his verse collections about Ms Gamba: we do not know if it was a case of sour grapes! In any case, the sexual woman as an operatic role first appears in the London stage parody The Beggars Opera by John Gay and John Christopher Pepusch in 1728.

In Elena, Menelaos, disguised as a woman, tries first to approach then to conquer the choice of his heart, the beautiful Helen, bringing men and women into sexual confusion. Much time had to pass from the situational comedies of early Baroque opera, from playful transvestism, until the operatic depiction of alternative gender tendencies. Although we can regard Tchaikovsky's operas as sublimations of this kind, it was Britten who consistently transformed homosexual, indeed paedophilic inclinations – partly "hidden" from legal sanction of the time – into high art (Peter Grimes (1945), Billy Budd (1951), The Turn of the Screw (1954), Death in Venice (1973). In an era when gayness was acceptable (and within an accepting social structure), the long and bumpy path towards liberation also became an operatic theme, such as Stewart Wallace's opera celebrating the life of the gay right's figure Harvey Milk (1995) or Péter Eötvös's opera about AIDS, Angels in America (2004).

The vocal transsexuality of 17^th century opera – for example, the personification of comic old women by a tenor or partial change of gender identity through falsetto – was replaced in the 18^th century by the stylised "asexuality" bel canto (or "beautiful singing") in the art of the castrato. The magic of the castrati was not just the sound of a boy's angelic voice being projected with the power of a man but their exceptional virtuoso singing skills. This was not least because they could begin their vocal studies while still children, given that they did not have to wait for puberty, which would otherwise alter the voice. Owing to the lack of testosterone, their ribs stretched further, and this resulted in large lung capacities and strong breath control. Castrati attained astonishing pulmonary skills, capable of sustaining each single note for 70 or 80 seconds and adding coloratura in between.

Their asexuality was only conditional, since even though they could not beget children, some were capable of serving the pleasure of women (and some men). Because of their infertility, the church forbade them to marry (castration of children without medical reason was also, in principal, banned). By the same token, there has survived a decree from 1761 in which the senate of Hamburg, in view of his fine character and blameless life, permitted the "56-year-old eunuch" Filippo Finazzi to "copulate" with the widow of the Jersbeck blacksmith.

The question of physical love in its stripped-down form was first raised in Tannhäuser (1845/1861). Wagner, bowing to 19^th century prudishness, of course depicts in dark colours "the truest essence of love", contrasting it with the immaculate purity of Elizabeth. The flood of femme fatales culminating with Berg's Lulu (1937) began here in the cave of Venus. If not in the opera itself, in the prelude of Rosenkavalier (1911), before the curtain rises, Richard Strauss unmistakably depicts the sexual union of Marschalin and her young lover, Octavian. By contrast, in Shostakovich's Lady Macbeth of Mtensk (1934) adultery occurs so openly, and is accompanied with such musical vehemence, that Stalin, the communist dictator, expressed his highest disapproval. Ligeti parodies another sexual perversion, caricaturing the dominatrix in his "anti-anti-opera", Le Grand Macabre (1978/1996), in the figure of the sexually unquenchable Mescalina.

"I am a human being, I consider nothing that is human alien to me," said Terrence, the comic playwright of Ancient Rome. It is our good fortune that the masters of opera writing also have the same faith. Like every great artist.