New Yorkers love a good party. Add art, alcohol, and ambiance into the mix, and it’s a winning combination — especially for city museums looking to attract more diverse crowds.

It’s a distinctly New York phenomenon, and it has been popping up all over town. What makes them so popular? Museum fetes are to cash-strapped hipsters what Hamptons benefits are to their older, more monied counterparts.

“I think there are a lot fewer people going away to the Hamptons or to the Jersey Shore these days,” the co-chairman of a young art aficionados group, PopRally, Sean Egan, said. “Our audience doesn’t necessarily have the money, but they’re interested in art and want to get involved in the art community.”

Earlier this summer, Mr. Egan’s group hosted a casual gathering at the Museum of Modern Art, PopRally’s sponsoring organization. Tickets cost $10, and the event attracted more than 700 guests, organizers said. Partygoers, who were treated to an open bar and a free T-shirt, could browse the Douglas Gordon Timeline exhibit and listen to an electro-pop band, “Chicks on Speed,” perform live.

Often free or low-cost parties are less about cultivating young, would-be donors than they are about courting new fine-art audiences, Mr. Egan said. “We don’t look at this as a revenue stream,” he said. “We’re not looking for money. We want them, the next time they go out, to think about coming to our museum.”

Mr. Egan said museum parties offer a welcome break from the run-of-themill nightclub party. “It’s a different environment,”he said.”You’re hanging out with friends amid the finest modern art collection in the world. It’s a great combination.”

A spokesman for the Metropolitan Museum of Art, Harold Holzer, said museum parties are “proliferating.” The Met, which opens its rooftop sculpture garden on Friday and Saturday nights, is no exception. “What it is, is an effort by every museum to reach out and find and develop younger audiences,” Mr. Holzer said.

By using popular DJs to attract a scene, the Cooper-Hewitt National Design Museum has seen interest in its Design + DJs + Dancing party, which gets under way in its courtyard Friday nights through September 8.

“Many of the attendees may first come because they’re fans of a particular DJ, but then walk through the museum’s exhibitions and discover they’re fans of design as well,” the museum’s press manager, Laurie Olivieri, said.

A 23-year-old graduate student, Jessica Leber, last weekend attended P.S. 1 museum’s “Warm Up” in Long Island City. Ms. Leber said she liked the downto-earth atmosphere of the party, which featured food, drinks, and a DJ spinning funk music. “There was definitely an artsy vibe,” she said. “I liked the setting a lot because you got to enjoy the art, the food and the music.” Admission is $10.

P.S. 1 has been hosting “Warm Up” parties Saturdays throughout the summer for the past decade, according to the museum’s director of communications, Yng-Ru Chen. While in its early days, the event would attract several hundred people, this year’s inaugural bash brought out about 6,000 people, Ms. Chen said.”It really becomes a destination for people in New York and for people who visit New York, as it’s received a lot of attention internationally,” she said. “You can just take the train over the bridge and have a nice afternoon party. We attract a very culturally conscious audience, and they’re generally pretty young.”

Voted the “Best Club” in 2005 by Time Out New York, the party grows significantly each year.”I went to for two or three years, but then it got so crowded you couldn’t get in.The crowd also started to get younger,” a former Williamsburg resident who now lives in the East Village, David Del Vecchio, said.

He noticed the hipster Williamsburg contingent growing stronger, but he also suspects the crowd may evolve again.”Now it seems that the scene has moved to McCarren Pool. They won’t even have to trek up to Queens. It’s right in their neighborhood,” he said.

Indeed, the free concerts at the Mc-Carren Park Pool, which occur on Sundays, increased in popularity mainly for the unexpected and slightly gritty atmsophere. Who wouldn’t want to boogie in a drained pool? It may be less artsy, but it’s still a creative crowd. According to a Williamsburg resident, Mark Stockton, the formula for the party’s popularity is simple: “It’s free. It’s in the sun — and there’s dodgeball.”

This is the second of a two-part story.