AT 11 p.m. on a recent Friday, the crowd at Brute on 9 in Tarrytown was starting to thicken. In the dimly lighted room, couples huddled together, while larger groups clustered around tables and a few dozen patrons congregated by the bar. Some nursed martinis in a variety of colors, others drank beer or wine; most were younger than 30, dressed in jeans and sweaters. Rock music playing at a comfortable volume underscored the sound of talking and laughter. At Lucy’s in Pleasantville, people also seemed in fine spirits, relaxing in high-backed booths and on black leather couches. Here, too, martinis seemed the drink of choice, perched beside candles on low glass tables. The music was more mellow than at Brute, and the age span broader, but the atmosphere was similarly friendly and laid back. Meanwhile, at Teddy’s, the lounge at the Holiday Inn in Mount Kisco, John Zacchio, a k a Johnny Z, was spinning oldies for 150 guests, an older group with a fair share sporting gray hair. Some sat at the bar or settled into couches and comfortable chairs that lined the room; others packed a small dance floor to cha-cha, fox-trot and twist under disco lights and a mirrored ceiling. In a county known for its schools, upscale homes and family-friendly suburbs, the existence of a late-night lounge scene may seem unlikely — and an unlikely choice for an evening out. But these three establishments offer adults of any age a place to socialize — to have a drink, unwind and maybe even join a line dance — without feeling like a parent at a teenage party. “We attract a more mature, sophisticated clientele,” said Sam Cucinell, manager of Lucy’s, which opened two years ago and caters to people who are 23 or older. “There’s more of a Manhattan feel here. We don’t serve food, but we stock better wines, and you can have a good martini.” A good martini nowadays means any of an array of customized concoctions, with ingredients ranging from garlic-stuffed olives to drizzled chocolate — a far cry from the traditional gin and vermouth. Just as Starbucks has transformed coffee into a decadent dessert, martinis have taken on personae as varied as Lucy’s Chai Martini, made with vodka and Voyant Chai Cream, and — at Brute on 9 — Jenny Craig’s Nightmare, combining butterscotch schnapps, crème de cacao and Baileys Irish Cream. The martinis at Brute are poured behind the bar but shaken at the table. Billy Turiano, the owner, said his biggest seller is the Brutini, made with Stoli Vanil vodka, Kahlúa coffee liqueur, Frangelico hazelnut liqueur and a shot of espresso. “We can make it decaffeinated,” he said, “but if you really don’t want caffeine, you have to nix the Kahlúa, too.” Andrew Murphy, a bartender at Lucy’s, has created Murph’s Cadillac Margarita, made with Don Julio Tequila Silver, Cointreau, Grand Marnier, sour mix, fresh lime juice and a dash of orange juice. Brute pays tribute to its Westchester roots with the Hudson River, a martini described as “nice and dirty,” and Teddy’s has its Legends of the Hudson Valley Applejack, a mixture of Jack Daniels and cider. Open from early evening to early morning, Brute on 9 and Lucy’s cater to an assortment of visitors throughout the night. “Older patrons come in earlier, and as the night gets later, the patrons get younger,” said Mr. Turiano, noting that Brute also attracts employees from nearby restaurants. “They come here when they get off work around 2 a.m. That’s when they start their happy hour.” Mr. Cucinell gauged the age range at Lucy’s from 23 to 60, with the majority being “a corporate crowd of young professionals.” “People come in before and after dinner, or after a show,” he said, referring to numerous restaurants in town and the Jacob Burns Film Center, down the street. What was once a neighborhood clientele, he said, has grown to include customers from around the county. “On a weekend night, there might be 100 people here,” he said. Lucy’s, which is about 2,000 square feet, consists of two rooms and a heated patio. Its wooden bar is flanked by two flat-screen television sets. Along with its couches are ottomans covered in sand-colored velvet and shaped like cubes and cylinders. Hungry patrons are offered takeout menus from nearby restaurants, and Lucy’s places their orders. Wednesday is occasionally a speed-dating night, and live bands perform every Thursday. “Even when it’s really busy, it’s a nice crowd,” Mr. Murphy said. Like Lucy’s, Brute is designed to create a welcoming ambience conducive to mingling. Its L-shaped bar sits in a corner, lighted by hanging bulbs shaded with cones of frosted amber glass. A few Hopperesque paintings adorn the walls, and the room, which is barely 1,000 square feet, is filled with tables and chairs. Brute, too, keeps a pile of takeout menus on hand for customers who want a bite; the bartender places the order, and when the food is delivered, provides plates and utensils at the table. Though Mr. Turiano considers Brute a lounge, there are no couches here. “That was deliberate,” he explained, “because at 4 a.m., couches make it a lot harder to get people to leave.” With an eye toward community service, Brute is sponsoring a holiday toy drive. “Beginning after Thanksgiving, if you bring a gift, you get a free beverage,” said Mr. Turiano. A fund-raiser for a local animal shelter is also planned. It is the unassuming Teddy’s, though, that tops the communal charts. During the week, it is a low-key hotel lounge, where guests might shoot a game of pool or watch televised sports at the double-sided bar. Cloud-shaped mirrors and cartoonlike murals add to a décor that may best be described as kitsch. But on weekends, the scene is transformed as people fill the 2,700-square-foot room, and music beckons them to dance. On Saturdays, a D.J. plays Top 40 hits, or occasionally a live band performs. Next January and February, the club will present a Saturday night comedy series. On Fridays, it’s Johnny Z’s “Nostalgic Sock Hop,” as Mr. Zacchio has dubbed it. It’s a gig that Mr. Zacchio, who grew up in Yonkers and has worked as a D.J. for 25 years, has had for four years. From May through September, it is preceded by a car cruise, during which classic-car enthusiasts display their automobiles in the parking lot. In true D.J. fashion, Mr. Zacchio, known for his Sunday night “Rock ’n’ Roll Revival Show” on WFAS-FM, uses his microphone to greet guests, dole out song trivia and introduce his next tune. Occasionally he joins his wife, Linda, and a group of regulars on the dance floor. (The couple met at Teddy’s and were married in September.) “I’ve been dancing all my life,” he said. “I smile a lot when I’m doing it” — as do the rest of the dancers, an unpretentious group ranging in age from 30 to over 60. As one song melds into the next, they shift from the Lindy to cha-cha, then rearrange themselves into a spontaneous line dance. Groups of women join together, and dancers spill from the dance floor onto the carpet when they run out of room. Those who want a snack can help themselves to popcorn from an old-fashioned movie-theater-style machine in a corner of the room. “Johnny Z has quite a following,” said Tom Traynor, of Yorktown, as he led his wife, Laura, off the dance floor. “We’ve been coming almost every week for the past three years. It’s a lot of fun.” If You Go BRUTE ON 9, 17 North Broadway, just north of Main Street, Tarrytown; www.myspace.com/bruteon9 or (914) 703-6022. Open Tuesday to Saturday, 7 p.m. to 4 a.m. (earlier if it’s a slow weeknight); closed Sunday and Monday. Martinis, $8 to $9.50; Brute’s Brews, $5 to $11; Wine by the glass, $6 to $7.50; bottles, $24 to $27. Espresso, cappuccino, tea and bottled water also available. No cover charge. Private parties for up to 35. Street parking. LUCY’S, 446 Bedford Road, Pleasantville; www.lucys-lounge.com or (914) 747-4740. Open Sunday to Thursday, 4 p.m. to 3 a.m.; Friday, 3 p.m. to 4 a.m.; Saturday, 5 p.m. to 4 a.m.; closed Monday. Martinis, $8.50 to $10; beer, $4 to $5; wine by the glass, $6.50 to $8; bottles, $25 to $28, with a Veuve Clicquot for $80. Happy hour Monday to Thursday, 4 to 6 p.m., with $1 off all drinks; Friday happy hour, 3 to 6 p.m., includes appetizers and $3 Stella Artois drafts. No cover charge. Private parties for up to 100. Parking on the street or in the lot behind the building. TEDDY’S In the Holiday Inn, 1 Holiday Inn Drive, Mount Kisco; (914) 241-2600. Open Monday to Thursday, 4 p.m. to midnight; Friday, 4 p.m. to 1 a.m.; Saturday, 4 p.m. to 2 a.m.; Sunday, noon to midnight. Mixed drinks, $7; beer, $4 to $5.25; wine by the glass, $5.25 and up. Friday: Johnny Z’s Nostalgic Sock Hop, 8 p.m. to midnight. Saturday: D.J., 9 p.m. to 2 a.m. No cover charge. Parking in the hotel lot or on the street.