A stretch of Park Avenue is one place where the necessity of public art comes into question right now. There a series of monumental, bulbous figures clad in colorful mosaic tiles by Niki de Saint Phalle (1930-2002) punctuates the traffic islands from 52nd to 60th Streets. Dating from 1983 to 2001, they include simplified but recognizable portraits of Miles Davis and Louis Armstrong, as well as a number of renditions of curvy, knob-headed female beauties and a stout tree whose branches have morphed into gold heads of lively snakes.

Back in the ’60s, when Ms. de Saint Phalle was developing her aesthetic, figures like these had a goofy, liberationist vibe. But the works here seem woefully outdated, more tacky than visionary.

As a counterpoint to Ms. de Saint Phalle’s strenuously playful works, a quartet of abstract metal sculptures by John Chamberlain occupies the plaza of the Seagram Building, on Park Avenue between 52nd and 53rd Streets. Made from 2008 to 2010, they are unlike the Abstract Expressionist conglomerations of automobile body parts he was known for.

Mainly they consist of tubular elements, made of crushed sheet metal, that resemble elongated elephant legs bound together into knotlike configurations. They were copied from small maquettes that Mr. Chamberlain created by molding aluminum foil with his hands. Colored metallic green, copper and silver, they are weird hybrids of beauty and ugliness. Here on the Seagram Building’s porch, they call to mind the old dismissive label for abstract sculpture on corporate plazas: “plop art.”

As chance would have it, there is a piece of outdoor sculpture in the same neighborhood representing the opposite of the beautifying imperative. Installed on the plaza of Lever House, it is a giant rat, one of those balloons that labor union strikers often bring with them to represent masters of the capitalist universe, but here cast in bronze by the team of young artist-provocateurs known as the Bruce High Quality Foundation. In a poetically just world, it would be permanently installed on Wall Street within waving distance of the raging bull.

The rat, titled “The New Colossus,” accompanies an exhibition of the group’s works in the glassed-in lobby of Lever House. It consists of real objects, like mops in buckets, vacuum cleaners, a step ladder and office furniture, scattered about the space. Each has an audio speaker built into it that is connected by radio to a video montage on a flat screen called “Art History With Labor: 95 Theses.” Different professional actors’ voices enunciating texts about art and labor emanate from the speakers, as if these objects associated with daily work had themselves become animated, like ventriloquists’ dummies, by unionizing passions.

I wonder what the denizens of this zone of corporate business and super-expensive domiciles think about the Bruces’ agitprop? It is hard to imagine many of them being aroused to revolutionary fervor. Still, the incongruity itself is refreshing. In this respect it is worth noting that the Lever House art program is privately sponsored, with the former Whitney Museum of American Art curator Richard Marshall organizing its exhibitions. It is rare to find such baldly partisan expression as the Bruces’ in outdoor art sponsored by public institutions. Offense is so easily taken, especially if taxpayer money is involved.

A more circumspect approach to political art can be found in two pieces included in “Common Ground,” a 10-artist exhibition in City Hall Park in Lower Manhattan, organized by the Public Art Fund. “It’s Never Too Late to Say Sorry,” by the team Elmgreen & Dragset, consists of a glass case displaying a gleaming aluminum megaphone. The case is locked, but a descriptive label explains that once a day a performer will open it and “activate” the piece. No actor showed up while I was there, but in an online video of the sculpture’s debut in Rotterdam you get to see a man unlock the case, take out the megaphone, hold it to his mouth and cry out, “It is never too late to say, ‘Sorry!’,” whereupon he returns the bullhorn to its case and walks away.

Placed across the park’s circular central plaza is Amalia Pica’s “Now, Speak!,” a podium cast in concrete that seems to invite people to step up and say whatever is on their minds. Otherwise implacably silent, it shares with Elmgreen & Dragset’s piece a funereal feeling. Both could be memorials to the loss of a widely shared and well-developed public discourse.

As Martha Schwendener observed in her review in The New York Times, other works in “Common Ground” exemplify the distinctive language of high-end contemporary art. Paul McCarthy’s colossal inflated ketchup bottle; Christian Jankowski’s plaque announcing the burial of his remains somewhere in the park; Justin Matherly’s rough re-creation of a part of the Ancient Roman sculpture “Laocoön and His Sons,” elevated on a platoon of aluminum walkers: these as well as works by Matthew Day Jackson, Thomas Schütte and Jenny Holzer speak in tongues likely to be as mystifying to the public as they are familiar to people conversant in the polyglot lingo of today’s art world.

There is another, more democratic — utopian, even — rationale for presenting this sort of art to the public. It might interrupt the usual flow of collective consciousness, diverting minds from routine compliance with the banal order of things and opening up ordinarily hidden vistas of imaginative vision.

A more viewer-friendly example of that approach is an installation called “Pet Sounds” by the sculptor Charles Long at Madison Square Park in Manhattan. The main elements are large, cheerfully colored fiberglass blobs resembling extraterrestrial or subaquatic life forms as imagined by the makers of “Ghostbusters.”

Some stand on their own; one sits on a park bench; another sprawls on a picnic table. All are connected to swerving hand railings that create winding pathways for visitors. A close encounter with any of the blobs reveals that each is equipped with a small speaker that emits futuristic electronic noises. A kind of surrealistic petting zoo with a nod to the Beach Boys, Mr. Long’s creation requires little esoteric knowledge to enjoy. Its generosity of spirit is infectious.

Although very different in style from Mr. Long’s sculpture, works by Oscar Tuazon in Brooklyn Bridge Park also aim to tweak everyday consciousness. “People,” the most complex of three pieces there, consists of a poured concrete handball wall with a tall dead tree attached to one vertical edge and an old basketball hoop and backboard attached to a truncated branch. Placed near a chain-link fence setting parkland off from an adjacent construction site, it looks less like art than like an ad hoc construction waiting to be broken down and carted away by a demolition crew. Another production of the Public Art Fund, it reflects a considerable uncertainty about who it wants its public to be.

You might suppose that the High Line would be a good site for outdoor art. Thus far, however, the park’s public art program has done little to distinguish itself. This summer’s effort, called “Lilliput,” sounds like a good idea. Organized by Cecilia Alemani, the High Line’s art curator, it presents small-scale sculptures by six artists distributed in inconspicuous places to either side of the main walkway.

Only one piece creates the sort of surprise you would hope for: Tomoaki Suzuki’s “Carson,” a startlingly realistic, two-foot-tall portrait of a young man with bleached hair wearing tight black jeans and a black motorcycle jacket. Made of carved and painted wood, this miniature hipster stands nonchalantly on gravel between old steel train rails, oblivious to the giant tourists who gawk at him or stop to pose next to him for snapshots.

Nothing else in “Lilliput” has such a galvanizing relationship to its environment. Though mildly appealing, Francis Upritchard’s Rodinesque pair of bronze simian creatures and Oliver Laric’s colorfully striped cast resin portrait of Sun Tzu with two faces like the Roman god Janus, would be seen to better advantage in an indoor gallery.

The High Line public art program faces an unusual challenge. The site is almost a mile and a half long but mostly no wider than a one-way street, and grass and other plantings take up a lot of that space. Because of its popularity, it is pretty congested in nice weather. With vendors selling drinks and snacks, as well, and so much nonart to see in different directions near and far and up and down, there is almost too much going on. Does the High Line need art on top of all that? I’m not convinced that it does.

Site Specific

 

BRUCE HIGH QUALITY FOUNDATION: ‘ART HISTORY WITH LABOR’ Through Sept. 28. Lever House, 390 Park Avenue, at 53rd Street; leverhouseartcollection.com.

‘COMMON GROUND’ Through Nov. 30. City Hall Park, between Broadway and Park Row, Lower Manhattan; publicartfund.org/commonground.

JOHN CHAMBERLAIN Through Nov. 16. Seagram Building, 375 Park Avenue, between 52nd and 53rd Streets; gagosian.com.

‘LILLIPUT’ Through April 14. The High Line, six sculptures between 30th and Gansevoort Streets and 10th and 11th Avenues, Manhattan; thehighline.org.

CHARLES LONG: ‘PET SOUNDS’ Through Sept. 9. Madison Square Park, 23rd Street between Madison and Fifth Avenues; madisonsquarepark.org/art.

NIKI DE SAINT PHALLE ON PARK AVENUE Through Nov. 15. Park Avenue between 52nd and 60th Streets; nikidesaintphalle.org.

OSCAR TUAZON: ‘PEOPLE’ Through April 26. Brooklyn Bridge Park; entrance at Old Fulton and Furman Streets, Dumbo. publicartfund.org/oscartuazon.