Apple’s iPod is still king of the digital music world despite increasing competition, according to a new report from the NPD Group. The research company said in a report released today that various versions of the iPod account for 92.1 percent of the market for hard-drive based music players, up from 82.2 percent a year ago. NPD said Creative and Rio were a distant second and third, with 3.7 and 3.2 percent of the market, respectively.