LOS ANGELES (AP) -- Google unveiled its much-anticipated digital music store Wednesday, opening a new front in its battle with Apple to provide services over mobile devices.

For the first time, Google Inc. will sell songs on the Android Market, its online store for apps, movies and books. The service is available over the next few days to customers in the U.S., but it aims to roll it out eventually to some 200 million Android users globally.

Some songs are free, while others were priced at 69 cents, 99 cents and $1.29 _ the same prices as on Apple's iTunes. Artists whose work is available right away include Adele, Jay-Z and Pearl Jam. The store will feature dozens of free tracks from artists like Coldplay, Rolling Stones and Busta Rhymes.

Google is offering 13 million tracks for sale, from three of the four major recording companies _ Vivendi SA's Universal Music, EMI Group Ltd. and Sony Music Entertainment _ and a host of independent labels. Warner Music Group was the major recording company left out. Warner spokespeople did not respond to requests for comment.

Google is allowing sharing of purchased songs over its social network, Google Plus. Friends will be able to listen to one another's songs once for free.

Once someone buys a song, it can be downloaded and is automatically uploaded for free into an online locker. The song can then be streamed over computer and mobile phone browsers, including the Safari browser, which comes on Apple Inc. devices such as the iPad. People who download the Google music app on devices running Android 2.2 and higher can stream stored songs or download them for offline playback within the app.

Google's director of digital content for Android, Jamie Rosenberg, took a dig at Apple's online song storage service, iTunes Match, which costs $25 a year. Google's cloud storage service is free for up to 20,000 songs.

``Other cloud music services think you have to pay to listen to music you already own. We don't,'' he said.

Recording company executives said that, although some of Google's features go beyond what is offered at iTunes _ specifically the one free listen for friends, the concessions were worth the benefit of reaching new customers.

``How many people do you know have both an iPhone and an Android device?'' said Universal's president of global digital business, Rob Wells. ``I encourage any new entrant into the digital music space who is going to help us reach a broad audience and sell legitimate songs.''

Mark Piibe, EMI's executive vice president of global business development, said Google's plan to bring legitimately sold music to people in new ways ``can only be good for the market as a whole.''

Although Google and the recording companies hope sharing of songs helps sell more tunes, some observers were skeptical.

Adam Klein, chief executive of discount digital music store eMusic, said that for his customers, buying music is more a considered, personal decision that is often not influenced by friends' tastes.

``A Google-Plus tie-in will not make it a game changer,'' he said.

T-Mobile USA, which brought Google's first Android-enabled smartphone to market in 2008, also was a partner in the Google music launch. The mobile phone carrier said it would offer other free songs to its customers and soon allow them to pay for music purchases through their phone bill.

Google also appealed to independent artists who release their own music, allowing them to upload songs, biographical information and artwork to the store after paying a one-time $25 fee. Artists would be able to keep 70 percent of all sales.

By launching the store, Google is opening its music service widely. It released the service as an unfinished beta in May to about a million people in the U.S. who requested an invitation and got one. That version of the service, which essentially uploaded your digital songs for online storage and allowed playback on computers and Android devices, proved to be a hit: Testers were streaming music on average 2.5 hours every day.