If you were asked to picture a scene from 18th-century France, you might summon the image of red-cheeked maidens frolicking in lush vegetation. Or, if you were thinking revolutionary thoughts, they might drift towards a tableau of sinewy men brandishing swords amid a battery of Doric columns. The source for that first posh and feminine vision is the rococo painter François Boucher; the author of the second is the austerely neoclassical Jacques-Louis David. Together, they have come to embody all of 18th-century French art, reducing that fertile time to a battle between frilly decadence and moral solemnity.

‘Mezzetin’ (c1718-20), by Antoine Watteau

This easy dualism, though, leaves out the bulk – and the best – of the period, which encompassed a wide range of emotion, mood, sensibility and intention. It excludes the incomparable master of ambiguity, Antoine Watteau, urban realists such as Louis-Léopold Boilly and Gabriel de Saint-Aubin, and the incipient romanticism of Hubert Robert and Pierre-Paul Prud’hon. Fortunately, New York now offers three exalted vantage points from which to take in the breadth and quality of the century’s art. The Met’s intimate Watteau, Music and Theater focuses narrowly on how the performing arts influenced the painter and, in doing so, lets us savour a world of melancholy pleasures. The Morgan Library’s Rococo and Revolution tracks the final, brilliant flaring of the old regime and the violent birth of the new one. The Frick’s gorgeous Watteau to Degas: French Drawings from the Lugt Collection takes an even longer view of French draughtsmanship, with well-chosen pieces by all the major players, as well as by the unjustly obscure.

Watteau, as mysterious and as provocative as ever, is the hero of all three exhibitions. His genius lies in the elusiveness that allows each generation to see in him a reflection of its own longings and aspirations. In the aftermath of his death in 1721, his immediate successors, Boucher, Lancret and Pater, tapped into the decorative and playful possibilities of his work. And yet those followers missed the subtle longing that lies at the heart of Watteau.

The Met displays his canvas “The Perspective” in the company of Lancret’s “Dance Before a Fountain”. In Watteau’s painting, several couples disport themselves against a backdrop of immensely tall, shimmering trees. A musician in the foreground provides the soundtrack for each pair’s private drama; quiet gestures signal varying degrees of closeness and connection. But the two central figures turn away from us. We see only their eloquent backs, though we can follow the presumed direction of their gaze down a narrow allée, towards a shimmering Palladian villa in the distance. The plotless painting typifies the genre Watteau invented – the fête galante, where aristocrats decorously trifle with one another in glorious gardens.

Following Watteau’s example, Lancret also includes the carousing couples, the musical accompaniment, the fluttering leaves and the snippets of classical architecture. He even apes the master’s silk gowns and glossy dogs. But Lancret reduces his ingredients to a predictably pretty brew. Watteau has something more profound to say: the dark sweep of his trees, the waning light, and the elegant arabesques formed by his figures speak wistfully of love’s transience and the fleetingness of life itself.

Watteau’s “decadent” subjects rendered his style anathema to the neoclassical crowd – David had no patience for his glorification of leisure. It took another couple of generations to find a fresh audience. In the 1860s, the bohemian circles of Théophile Gautier, Gérard de Nerval, Charles Baudelaire and others responded to his gossamer evocations of late afternoons and to his life as a tragic genius. Gautier observed that, in spite of the lightness of his hand, “Watteau was an invalid and melancholy, saw the dark side of everything, and had no rose colour save on his palette”. They saw a reflection of the artist’s predicament in the figure of Pierrot, the sad clown from the commedia dell’arte whom Watteau rendered with near-obsessional frequency. In the “Italian Comedians” at the Met, the spot-lit Pierrot, his face encircled by the halo of his golden cap, evokes the risen Christ himself in all his sad and beatific glory.

‘Comédiens italiens’ (c1719-20) by Watteau

If 19th-century aesthetes saw Watteau’s lost paradise as a seductive retreat from the modern world, their 20th-century counterparts discovered in him the very essence of modernity. Picasso, in particular, savoured Watteau’s mute commedia dell’arte characters as the personifications of existential absurdity. His cubist “Harlequin” from 1915 is an alienated freak, with jagged edges and a ghastly smile. A decade later, in an overt nod to Watteau, Picasso painted his son Paulo in Pierrot’s white suit, with a deadpan expression and a double corona of red hair and black hat.

Picasso probed a gap he perceived between the elaborate theatricality of Watteau’s tableaux and the kernel of psychological intensity. Watteau’s portrait of the guitar player Mezzetin, the star of the Met’s exhibition, has a cinematic sweep. The instrument’s quiet plucking has generated a whole panorama of mournfulness: the lustrous silk of his outfit, concentric circles of brooding vegetation, a poignantly shadowed statue in the middle distance, the woebegone tilt of the protagonist’s head.

All the posing and décor distract from the genuine misery stamped on the musician’s face, which becomes more blindingly obvious in a breathtaking chalk study of the same character. The sketch could have been made a month ago, so immediate and modern does it seem, so absorbed is the artist in the stubbled cheek and glazed eyes. This is no grease-painted entertainer but simply an unhappy young man, like the one who sat across from you in the tube this morning, or the adult child you wish you could succour. It’s not just the models who are dressed up and directed in Watteau’s costume dramas; his sense of empathy also wears a dandy’s exquisite disguise.

Met show runs until November 29, tel +1 212 535 7710;
Morgan Library’s until January 3, tel +1 212 685 0008;
and the Frick’s until January 10, tel +1 212 288 0700