Microsoft said Friday it plans to release a new music and entertainment player and accompanying software under the “Zune” brand this year, in a belated attempt to challenge the dominance of Apple’s iPod player. The announcement comes after weeks of rumors and speculation about such an offering. The iPod holds more than half of the digital media player market, according to research company NPD, while iTunes accounts for over 70 percent of U.S. digital music sales. In the United States, the iPod has more than 75 percent of the digital music player market, according to NPD.