LOS ANGELES — Allen Klevens and Jason Shapiro don't spin vinyl at parties or nightclubs, but they just might be the ultimate DJs.

If you've checked into a Marriott recently, eaten at Wolfgang Puck's Cut or gotten a facial at Spa Nordstrom, you've probably heard their mixes.

It's a science, said Klevens, a former musician who started his business, Prescriptive Music, by compiling and peddling soothing CDs for surgeons to play in operating rooms.

Today, Klevens and Shapiro help hotels and restaurants create a vibe. Don't think it matters? Listen to the music next time you're out to dinner or checking into a resort.

"Music sets the tone for any place — whether you're in the car, whether you're in the home or in a hotel," said Klevens, 34. "However the client wants them to feel, we can portray with music."

Too loud and it overtakes conversations. Too soft and it adds nothing. If it's the morning, it should be mellow. Think Michael Buble and Norah Jones, not The Rolling Stones or Madonna, who are better suited to the afternoon.

"You notice it when it's not good or you notice it when it's not there," said Klevens, sitting with Shapiro in The Blvd restaurant and lounge at the Four Seasons Beverly Wilshire in Beverly Hills. "Put it back on and it changes the whole vibe."

To make their point, they tap into their laptop wired into the hotel's sound system and turn the music off.

In an instant, the room turns loud and hectic — lots of jumbled conversation and noise. Music, they contend, can make all the difference.

Unlike Muzak, whose playlists cannot be altered on site at a moment's notice, Prescriptive Music offers clients a licensed on-demand music system, which allows them to hear what they want, wherever and whenever they want. They also can manipulate playlists to delete songs or play them at a specific time.

A pianist since age 4, Klevens said music was "in my blood." But after graduating from the University of Nevada, Las Vegas with a degree in music and communications, he didn't have a plan for how to turn it into a career.

For a while, he sold pianos and television advertising time. Neither made him happy. One day, bored, he went with his dad to a convention for the American Association of Operating Room Nurses.

One booth had people lined up to buy a CD, "Music for the O.R.," and the idea hit him.

He formed Prescriptive Music in 1999, with the slogan: "Bringing music to health." He compiled six CDs, finding musicians to create and record music suitable for doctors. One album was a mix of piano and cello music. Cellos are the closest instrument to the human voice and relaxing in tone, Klevens said.

At a trade show, he met someone who introduced him to The Venetian resort's Canyon Ranch SpaClub.

The Las Vegas spa wanted a new CD and new packaging. It became Klevens' first private-label CD, tailored specifically for the destination. The Venetian began leaving the CD on pillows in some of its suites. Pretty soon, other spas and hotels started calling Prescriptive to do the same thing for them.

Klevens and Shapiro sift through Internet sites such as MySpace and Facebook for emerging artists, and they sign musicians from other countries. Often, customers don't want recognizable songs. They want music that sets a tone and reinforces the message of the place.

One mountain spa in Utah, for example, asked for yodeling. "I tell you, we scoured everywhere, and we found it," Klevens said.

Klevens struck up a friendship with Shapiro through their children, and, in 2005, they teamed up. Shapiro, a former baseball player in the Chicago White Sox farm system and a real-estate lender, helped focus on the business side.

Sales in 2006 ballooned by nearly 300 percent to $1.35 million. They expect to double that in 2007.

With six employees, including an art director, music director and salesperson, their team is "lean and mean," Shapiro said.

The business has branched out well beyond branded CDs. In September, they pioneered what they call "On Key," packaging a CD with a special slot for a hotel key. The CDs are given to guests when they check in. The Flamingo casino in Las Vegas rolled out the CDs as part of their new "Go Rooms" with flat-panel televisions, iPod docking stations and a CD and DVD player. Among their other clients are San Diego's new Ivy Hotel and the Noble House Hotel & Resorts, which has 11 properties in the United States.

"We're pretty much redefining the Flamingo," said Jay Franken, vice president of operations. "We opened in the '50s and we were at the top, but it's gone downhill. Now we're trying to get it back on top again."

With hotel guests, Franken said, "You only have one chance at a first impression." Customers checking into the renovated rooms are handed their key, tucked inside the CD case.

The case also contains a message from the Flamingo's president: "Settle in, unpack and enjoy the music!"

Once in their rooms, guests can listen to the music, which Franken describes as "down-tempo lounge music." The 15-minute CD includes three mixes and a fourth song by Nils Lofgren, the guitarist from Bruce Springsteen's E Street Band.

"The guests love" the CD, Franken said. "A lot of people are taking it with them. We're not getting very many of them back. And customers are asking, 'The music's cool, can we get more?' "

Flamingo might have Klevens and Shapiro put together a full CD of 20 tracks and offer it for sale in the hotel's gift shop.

As part of their consulting, Klevens and Shapiro usually tell hotels to turn up the volume. The music is zoned into chunks of time and types of music.

Besides the private-label and On Key CDs, Prescriptive Music offers music consulting and custom playlists. Right now, they're helping Marriott International Inc. install music systems at 400 hotels across the United States.