Apple, which introduced a new line of iPods in early September,has managed to stay one step ahead of the competition--so far.
"One thing that has set Apple apart from its competitors is its ability to define the rules of the game," says Andrew Neff of Bear Stearns.
Though Apple dominates the digital music world, it is increasingly being challenged by such heavyweights as Sony, Nokia, Yahoo and Amazon.com .
Sony, for instance, recently launched a new U.S. version of its Sony Walkman that includes the ability to play digital video. Nokia the world's largest maker of mobile phones, unveiled an online music store and new high-end handsets with music and video game playing capabilities. And Yahoo is offering an unlimited music subscription service to rival Apple's iTunes.
Microsoft, meanwhile, said this week that it will start selling three new Zune models in mid-November. The 4-gigabyte, 8-gigabyte and 80-gigabyte Zunes will all come with a new feature that allows a user to wirelessly and automatically sync media via a WiFi network from a PC to the Zune when its battery is charging.
The Wall Street Journal reports that Microsoft revamped its family of Zune digital-music players and software, in an attempt to compete more seriously with Apple's iPod this holiday season.
The new Zune products are smaller than their predecessors, have better screens for watching video and include new features, such as one that will let users wirelessly synchronize the devices with music on a personal computer.
But the devices, don't appear to offer any radical breakthroughs that suggest an imminent threat to Apple's thriving iPod busines.
Threat From Amazon
Meanwhile, Amazon launched a revamped music-downloading service last month, posing what may be the most serious threat to Apple.
"That's one to keep your eye on," says NPD Group's entertainment analyst Russ Crupnick. "You have potential with Amazon because music aficionados like Amazon from buying the physical music and they like the Amazon model. The more simplicity there is, the more chance there is the barriers that Apple has built up may start to fall a little bit."
Despite this growing threat, most stock pickers are bullish on Apple's prospects. About three-quarters of all the analysts who cover the stock rate Apple at "outperform" or better, according to Thomson Financial. And the stock has not disappointed investors, sporting year-to-date gains of more than 60%.
Apple has kept a stranglehold on the music-downloading space, maintaining a market share of about 70% over the last few years for single-song downloads, according to data culled by research firm NPD Group.
Music sales through iTunes make up just 11% of Apple's $5.4 billion in quarterly revenue but the service is seen as a synergistic with its bread-and-butter iPod hardware business.
"Apple is the only one that has hit on the holy trinity of software, a store and hardware," says Crupnick. "Apple has created an ecosystem with the iPod where customers manage all their music through iTunes, buy music through iTunes, which all works well with the iPod."
Moving in on Apple's Turf
Still, more companies are trying to move in on Apple's turf. Viacom's MTV Networks recently combined its online music store Urge with RealNetworks' music subscription service. The new service will be accessible from computers or portable devices and will also be integrated with the Verizon's VCast cell phone service.
Vivendi's Universal Music also is testing the sale of songs without copyright protection through outlets such as Google, Wal-Mart Stores and Amazon.com, a move that some analysts say may change the current paradigm.
For Yahoo , which offers an unlimited music subscription service, it is somewhat unclear how lucrative the online downloads business is.
"I'm not sure anybody is making a whole lot of money," says Crupnick. "If you were to look at some of the financial statements it's been a real challenge for everyone whether it's a subscriptions model or a hybrid like eMusic."
Despite all the competition, investors should buy Apple shares, advises Pacific Crest Securities' analyst Andy Hargreaves. The company, he says, "has a tendency to go above and beyond people's expectations."
Even so, Hargreaves expects Apple's product announcement to be "fairly minimal" to the company's long-term picture.
"We would be buying it for the Macs, the iPhones and the iPods," he says.
Peter Kang is a markets reporter at CNBC.com. He can be reached at email@example.com.