It was another typical Friday night in Brooklyn, as a middle-aged husband and wife, tired from the workweek, settled into their domestic routine.

“Mic check, one, two,” Roberto Williams said from his office, while Zaida Soler-Williams cleared a refrigerator shelf in the kitchen and arranged microphones on a coffee table in the living room. A fireplace with lapping flames played on an oversize screen while two disco balls slowly rotated.

Soon, their home would be full of strangers belting out “Bohemian Rhapsody” and “Drops of Jupiter.”

As the proprietors and residents of Lion’s Roar Karaoke House, Mr. Williams, 52, and Mrs. Soler-Williams, 47, have hosted up to 30 singers and carousers at a time in their living room almost every weekend for four years.

They didn’t mean to start a karaoke club in their house. It kind of just happened.

In late 2012, the couple was lounging in bed, watching television, when they received a random phone call “from someone who said that he was with 10 other people and he would like to come over for karaoke,” Mr. Williams recalled. “I said, ‘I’m sorry, but you’re calling my house.’”

The caller had stumbled across an old website for Lion’s Roar Entertainment, a mobile, for-hire karaoke and D.J. business that the couple closed in 2008 — save for a rare gig here and there — to focus on their other careers. Mr. Williams was a vocal music teacher, and Mrs. Soler-Williams, a television postproduction supervisor.

But by the following weekend, more people were calling, eager to sing karaoke at their house.

“I don’t know what that one guy did, but he bumped Lion’s Roar Karaoke to the very top of the search engine somehow,” Mr. Williams said. “It was like the Google algorithm was suddenly in our favor,” Mrs. Soler-Williams said.

Within a few months, visitors started showing up at their front door (the old website also listed their mailing address).

After over three years of fielding calls and turning away visitors, the couple began to wonder if they were missing an opportunity.

“I’m a big believer in spirituality, and I said to Zaida, ‘Maybe somebody is trying to tell us something,’” Mr. Williams said.

“If you think about how the culture changed between 2013 and 2016 — I’m doing Uber shares, I’m sharing my home with Airbnb, I’m staying at Airbnbs myself, so suddenly it didn’t seem so strange to let strangers into our home,” Mrs. Soler-Williams said.

And so, the couple decided to join the ongoing D.I.Y. entertainment trend of people opening their homes to the public for concerts, plays, dinner parties, and cocktail clubs, by offering a karaoke option. They opened for business in March of 2016.

Lion’s Roar is pricier than many other karaoke bars; rates start at $125 per hour for 10 guests or fewer, along with a $25 cleaning fee (both amounts increase depending on the number of people in the party). But in exchange, amateur singers have access to a homier and more refined space than say, a sticky-floored private room or a tiny, harshly lit (and quite public) platform stage in a dive bar.

“We’ve always said that our brand was ‘klassyoke,’” Mrs. Soler-Williams said. “We’ve tried to bring some elegance to it.”

Just after 8, the buzzer rang. “They’re here!” Mrs. Soler-Williams said, as she opened the door to a group of 20- and 30-somethings who filed into the house, shedding bulky coats and stashing a bottle of vodka in the couple’s freezer.

Giuseppe Diprima, 36, was the party’s organizer. After nine visits to Lion’s Roar, Mr. Diprima has become something of a regular. “This is the only place I feel comfortable doing karaoke because I can’t sing,” he said from the kitchen, watching his friends place bottles of prosecco onto the empty refrigerator shelf. He pulled a wine glass out of a cabinet. “I make myself right at home.”

Considering the risks of hosting alcohol-fueled parties for strangers, the Williamses have been lucky. “I think we’ve had four or five bad incidents where things broke,” Mrs. Soler-Williams said, recalling a towel bar that got ripped out of the bathroom wall.

So far, they’ve had few noise complaints. It helps that they own their building, a three-story house on Meserole Street in Williamsburg, where they have installed a sculpture of a lion’s head and pink light bulbs over the front door.

They’ve never had to advertise and have never hired a cleaning service. “Our overhead is basically batteries, electricity, and pens,” Mr. Williams said. Food and drinks are B.Y.O.B., and music licensing fees cost just under $100 per quarter.

In 2019, they cleared six figures for the first time, making just over $15,000 in December, their busiest month, Mr. Williams said.

As Mr. Diprima’s party got into full swing, Mr. Williams served as D.J., announcing each singer, while Mrs. Soler-Williams attended to the guests, showing them to the garbage, refilling the ice bucket, and pausing to dance and sing along.

While two women sang Rod Stewart’s “Young Turks,” the couple took a break to eat their dinner — takeout fried chicken and rice — inside Mr. Williams’s office, which doubles as the D.J. booth.

The party was scheduled to end at midnight, so a few minutes before, Mr. Williams left his booth to perform “In the Air Tonight” by Phil Collins. The fireplace reappeared on the karaoke screen — he didn’t need lyrics. “From our house to your house,” he said after finishing the song, “we wish you peace, love, elegance and excellence.”

Once Mr. Diprima’s party had cleared out, the couple began cleaning in the event of any late-night drop-ins.

About 10 minutes later, the buzzer rang again. Mr. Williams, who was on his hands and knees polishing the black marble kitchen floor, called to his wife. “It’s clearly one of those nights honey,” he said. “We’ve got to be on our toes.”