Apple Computer continued to lead the U.S. digital music player market in the second quarter with a 75.6 percent share, according to the NPD Group."Apple has done a great job of focusing consumers\u2019 attention on digital music in their products through millions of dollars in advertising," said Ross Rubin, analyst at the NPD Group, via e-mail. But it\u2019s hard to tell if Apple will be able to maintain its sizable lead as mobile phone companies continue to put out handsets with built-in music players. A number of analysts have warned that the digital music player market could go the way of the PDA, which saw growth drop off once mobile phone companies introduced smart phones, handsets with PDA functionality.Rubin says that companies focused on standalone digital music players should remain competitive against the mobile phone industry because their devices have greater capacity, better user interfaces, better integration with online music services and stronger digital rights management support.U.S. mobile phone service providers have also hindered the popularity of using mobile phones as music players because they have been charging more for purchasing songs online than their rivals in the standalone music player business, Rubin said. Carriers have also in some cases been reluctant to enable music file exchange with PCs via memory cards or Bluetooth, instead preferring that consumers rely on their networks for purchases, he added.But he noted that mobile phone companies are getting better at the music business, especially in recent handset models from companies such as Sony Ericsson Mobile Communications, LG Electronics and Nokia, indicating that the fight is still in its early rounds.SanDisk followed Apple in the second-quarter ranking with a 9.7 percent market share, according to the NPD Group, while Creative Technology took third with 4.3 percent of the U.S. digital music player market.The NPD Group does not include mobile phones with built-in music player functions in its figures.-Dan Nystedt, IDG News Service (Taipei Bureau)Check out our CIO News Alerts and Tech Informer pages for more updated news coverage.