Google unveiled its much-anticipated digital music store Wednesday, stepping up the competition against the likes of Amazon and Apple. The new service features millions of songs from record labels EMI, Sony Music, Universal and several smaller labels, but is notably missing access to Warner Music Group's catalog. Apparently, the two couldn't come to terms regarding pricing and anti-piracy measures.

Users will be able to buy songs through the Android Market, with tracks costing somewhere between $0.69 and $1.29. To help jump-start the new music store, Google said it would offer one free song for consumers to download every day, while allowing them to share purchased songs with friends on Google+.

The search giant also announced that Google Music has graduated from its beta testing period and is now available for public sign-ups in the United States. The service includes an online storage locker where you can upload up to 20,000 songs you already own for free. Any songs you buy from Google's Android Market will show up in your online storage locker but it won't count against your 20,000 song limit.

Apple currently charges $25 annually for uploading and storing up to 25,000 songs not purchased through iTunes, while Amazon offers unlimited cloud music storage (plus 20GB for other files) for $20 a year.

Songs stored on your Google Music online storage locker can be streamed to any device via 3G/4G or Wi-Fi. Google Music stores the songs you've recently played in your cache so they're still available if you lose your Internet connection. You can also 'pin' songs, albums or artists you want to make available offline.

The new service will no doubt help Google promote its Android smartphone OS and marketplace, but it's not exclusive to the company's mobile platform. It will be available through the Music app on Android 2.2 and up, a Music Manager desktop app for Mac OS X, Linux, and Windows, and an HTML5 mobile Web app that can be accessed on virtually any device by visiting using a mobile browser.