Google has launched an online music store in the US, which will allow devices running its Android software to buy, store and stream MP3 files.

谷歌在美国发布在线音乐商店，允许运行安卓系统的设备购买、储存和分流mp3文件。

EMI, Sony Music Entertainment, Universal and 23 independent labels are providing content to create a library of 13 million songs.

However, Warner Music Group has opted¹ not to take part at this point.

The service poses a challenge to Apple's dominance of the sector². It launched its iTunes store in 2003.

The popularity of the iPod maker's mobile devices helped drive sales.

However, a new study by the research firm Gartner suggests that more than half of all smartphones sold between July and September ran Android. That accounts for more than 60 million devices.

By comparison Apple's iOS handsets accounted for 15% of the market over the same period, according to the study.

Social network

Google is also integrating（整合） its new service with its Google+ social network.

Users will be able to share songs with their Circles contacts who can listen to the full length of the tracks one time without making a purchase.

Songs range in price from 69 cents (44p) to $1.29 and come without DRM copy-protection. The search giant is also offering a different track free for download every day.

The firm announced it has secured exclusive（独有的） content.

The rapper Busta Rhymes - who was at the launch event - is debuting³ his new studio album on the Android store. The Rolling Stones and Coldplay are offering previously⁴ unreleased live performances.

Google is also hoping to link with smaller artists through its new Artist Hub. Musicians can add their own page for a $25 fee and set their own prices. Google will take a 30% share of each sale.

The firm did not discuss any plans to offer Google Music outside the US.