In Monster Field, 1938, fallen trees appear like the fossilised remains of giant creatures from prehistory. With great horse-like heads, and branches like a tangle of tentacles and legs, Paul Nash’s series of paintings and photographs serve as documents, bearing witness to the malevolent lifeforce that, unleashed by their undignified end, has taken hold of these apparently dead trees.

There’s something familiar about those dark, piercing eyes, but the impenetrable, mask-like countenance of Picasso’s Self-Portrait with Palette, 1906, is ultimately unknowable. In fact, the painting serves as something of a rebuke: we think we know Picasso so well, but we don’t. It’s a theme emphasised by the hang of this exhibition, and the bewildering range of styles and formats from Picasso’s early years results in a visual discord that underlines his chameleon-like tendencies.

Stravinsky's music, chameleonic yet always itself, offers so many lines of thought. One struck me immediately with the descending, even harp notes and tender, veiled strings at the start of his 1947 ballet Orpheus last night: the inexorable beat of time is so often pitted against an expressive, human voice. Esa-Pekka Salonen, who started out as a rhythm and textures man, now gets the humanity too.

Gorgeous, sumptuous, thrilling: here comes Abstract Expressionism riding into town, the first major overview in London since its own contemporary heyday in the 1950s. A clunky, unappealing label for such fabulously appealing stuff, it's best just to relax and enjoy this total immersion, for colour and gesture can never have been combined to such memorable effect. Nurtured by the melting pot of New York, this was the first homegrown group of American artists, its activities destined to put New York on the international culture map, wresting the crown of art capital from Paris.

Of all the mesmerising images in William Kentridge’s major Whitechapel show, the one that lingers most, perhaps, is that of the artist himself, now turned 60, hunched and thoughtful, wandering through the studio in Johannesburg where he lives and works. He paces, meditates over a "magical" cup of coffee, imagines, draws, tears paper, works, adjusts, observes, directs – all in the gentle manner of a Buster Keaton-style silent film star. Time in this metaphoric space is thick with possibilities, under-stated humour and conundrums.

If you’ve had half an eye on BBC Four’s conceptual art week, you’ll have noticed that the old stuff is where it’s at, with Duchamp’s urinal making not one but two appearances, equalled only by Martin Creed, that other well-known, conceptual stalwart (who actually isn’t as old as he looks). The BBC would say that this is because 2016 marks the centenary of Dada, the anarchic, absurdist art movement (if a movement is what it was) that saw artists begin routinely to challenge and ridicule accepted ideas about art – what it is, why it is and what it’s for.

Neon was once the triumphant glowing symbol of commerce and capitalism. In the 1930s the distinctive tube lighting gleamed above broadway theatres and on prominent billboards in the world’s great metropolises from New York to Paris. These glory days were not to last. Within just few years neon signs were removed from their downtown pride of place, demoted instead to apologetically jutting out from roadside motels and peripheral dive bars.

Bruce Chatwin’s sense of place stayed slippery. If he had roots, they were in the Black Mountains across the Welsh border, a fond childhood memory he deepened for his third book with the rich anecdotes buried in old newspapers. The tale this iconoclastic travel writer spun in On the Black Hill was of twin brothers, Benjamin and Lewis, who stay put in their patch of Wales as the 20^th century and its World Wars grind past them, like the noise of a car in the next field. Book and film are about lives in a landscape, each enriching the other.

Owen Wingrave is the Britten opera that always comes with a caveat, an apology. Dramatically flawed (a problem partially, but by no means entirely, accounted for by its genesis as a television opera) and musically uneven, it has nevertheless emerged recently as a favourite choice for young singers, with Guildhall (2013), the Royal Conservatoire of Scotland (2016) and now British Youth Opera (2016) all choosing to stage it, with varying degrees of success.

The jungle, a region of Edenic fantasy and unspeakable terrors, has always fed the white man’s imagination as well as kindled his greed. Not surprisingly, this is rich ground for the movies – a place beyond time, the home of noble savages and an El Dorado to be stripped of its riches. In most jungle movies, including The Mission and The Emerald Forest, the indigenous population is romanced or demonised, or a mixture of both.