For much of the 20th century, it was derided as the Spam of sounds, the pablum of music.

Yet in the 21st century, the South Carolina-based company that still calls itself Muzak has enjoyed some of the most profitable periods in its history, partly due to its willingness to change with the times.

"We don't have artists come in and do a light version of Led Zeppelin or whatever," Muzak spokeswoman Karen Vigeland said. "We use everything from Nirvana to Mozart to Britney Spears."

When people think of Muzak, they often think of cloying, boring, impossibly mellow re-recorded tunes, like a lighter version of a Celine Dion song. But Muzak stopped commissioning re-recorded versions of popular songs 25 years ago, and today you're more likely to hear an original song by an original artist as you shop in the supermarket or wait for the dentist.

And while a lot of Muzak's clients still like "soft relaxing sounds," adult contemporary is only one of about 100 programs.

"Most now are requesting a pop music and rock sound, of Top 40 and radio hits," Vigeland said.

Current Muzak artists include Gwen Stefani, Aerosmith, The Allman Brothers, Marvin Gaye, The Beatles, Elvis Presley, Aretha Franklin, Stevie Wonder, Run DMC, Kanye West, Maroon 5, Kelly Clarkson, Ludacris, Beyonce, U2 and, of course, Celine Dion.

Muzak has also added more musical genres to its oeuvre, including more electronic music, acid jazz, urban programs and especially world music. (There are other re-recorded music companies that followed Muzak, but Muzak has about 60 percent of the market share.)

And the variety has paid off.

"We're in 400,000 businesses around the world. We're in nine countries. We have 200 offices in the United States. We are in government offices to mortuaries to law offices to any type of office you can imagine," Vigeland said.

Muzak's roots go back farther than most people realize. In 1922, a retired major general, George O. Squier, patented the idea of using America's quickly sprouting power lines to transmit music.

In that same year, a public-utility holding company called North American Company picked up the rights and created Wired Radio, Inc.

Eight years later, homeowners in Cleveland were the first to enjoy piped-in music, courtesy of the Muzak Corporation — a name Squier generated when he combined the word "music" with "Kodak," a company he admired.

But, appropriately enough, the genre of almost offensively inoffensive tunes that would be hung with the moniker "elevator music" owed much of its growth to another invention that shot up during the early 20th century — elevators.

Many saw the claustrophobic newfangled transports as death traps, but America's rapidly changing cityscape demanded that Americans overcome their fears of the moving boxes.

"This was a situation where skyscrapers couldn't go up any higher without elevators, and required people to get into elevators to be packed in together for relatively long periods of time," said Arthur Gottschalk, professor and chairman of the music department at Rice University in Houston, Texas. "The only way to get them to do that was to pump music in there to stop fights from breaking out."

As America grew, so did Muzak, which was played at stores to provide soothing background music for shoppers and in workplaces to increase productivity. Suddenly, life had a soundtrack.

"Most people never gave a thought to why they were hearing Celine Dion or Neil Diamond," said David Allan, assistant professor of music marketing at Saint Joseph's University in Philadelphia. "These were just the things you heard while you were shopping or working. Studies showed that it made the retail experience better for consumers.

"In a workplace, when you played music, your workers seemed to be a little happier, crisper. Research says those things are improved by music. If you listen to happy music, you're a happier person."

Muzak became so commonplace that Americans began to see it as absolutely normal, according to Robert Thompson, professor of popular culture at Syracuse University.

"The idea of music as part of the architecture of a place we have come to take so much for granted that you don't even think about it anymore," he said. "The old days of hearing a Red Hot Chili Peppers song as a string version are probably over, but the concept of environmental music is absolutely never going to go away.

"If it ever went away, it would be really weird. We don't even realize how many places have this stuff playing in the background."

Of course, there were a couple hitches. For one, some people resented the idea of being manipulated by Muzak — even though the company has categorically denied ever using subliminal advertising.

For another, the vast majority of people thought the saccharine songs they were listening to in elevators and dentists' offices were fairly wretched. Within decades, Muzak went from being the cutting edge of music technology to being synonymous with the worst in listening experiences.

"In the '50s or '60s, the name started getting put into the elevator-music genre," Vigeland said. "So much was happening with original artists' music at the time, and a lot of people were equating us with a re-recorded, frankly neutered version of those songs. They didn't like it at all, and we started getting a bad brand connotation. It's something we're always going to have to deal with."

In 1998, the company completely overhauled itself, though it eventually dismissed the possibility of jettisoning the Muzak name.

It turned its focus toward audio architecture — the concept that what people hear at a location is just as important as the way the products are displayed, the color of the wallpaper or other elements of interior design, and a concept that Muzak itself had no small hand in developing.

Muzak installs, programs and maintains the music for businesses, updating song lists via satellite dish while handling licensing fees and using reams of painstaking research to figure out where every element is most effective.

It's also expanded their in-store messaging offerings and the kind of programming telephone callers hear when they're put on hold, and has branched out to handle televisions for, say, sports bars, installing plasma-screen TVs, piping in Dish Network sports packages, and so on.

And the new Muzak is working, the company says. The last three quarters of 2005 were most profitable in Muzak's history, Vigeland said.

Gottschalk doesn't foresee a future without Muzak.

"The needs for it haven't diminished any," he said. "If anything, we're packed into smaller and smaller crates, and it's one of the few things that works in keeping people distracted so they don't get upset with the guy invading your personal space. There may be a greater need for it now than ever before."