Like Spotify and Rdio, All Access includes songs organized by genre and artist that can be used on Android smartphones, Android-based tablets and desktop computers.
"Anything you can see, you can start playing immediately," Google engineer Chris Yerga said about All Access' music library. "[It's] radio without rules."
Few other details were revealed, but Yerga said All Access will provide recommendations based on the user's listening habits. The full catalog of music also will be mixed with the user's personal library of songs.
The announcement of All Access is expected to intensify the battle among subscription music services. Spotify boasts 20 million total users, with more than 5 million paid subscriptions. Rdio does not release numbers.
Google also announced enhancements to its Google+ social network, the competitor to Facebook.
The website's main design has been changed to multiple columns for posts that is more akin to a magazine layout.
"This new stream is about design and depth," said Google senior vice president Vic Gundotra. "We made sure [the new design] was fast, fluid and fun."
Users of the network also can upload their photos to Google+, where the images can be enhanced automatically to look better, and the network can pick the best pictures taken during an event and prioritize them automatically.
Other announcements made Wednesday during the event:
• Google introduced Google Play Game Services, a series of new features for gamers on Android mobile devices. They include the ability to save games in progress in the cloud so a player on one Android device can pick up where the game left off on another Android device. There also are new services for game achievements and leaderboards so players can boast their game-playing abilities, and for multiplayer matchmaking that automatically finds players online for a multiplayer game.
• The company debuted a version of the just-released Samsung Galaxy S4 smartphone that runs on an un-modified, pure version of the Android operating system.
Nearly all Android smartphones from manufacturers such as Samsung, HTC and Motorola come with versions of the Android OS that are heavily modified with tweaks made by both the handset manufacturer and the wireless carrier.
But this new version of the Galaxy S4 is a much-desired change because many of these modifications added to phones can slow them down or fill up the storage with unneeded applications.
• A new version of Google Maps is being developed with a new user interface and features that make it easier to find restaurants or points of interest. A preview will be available by invitation only beginning Thursday. A new version for mobile apps is expected this summer.
• A new Hangouts app is available for iPhones and Android phones in which users can exchange messages and have video conversations across multiple platforms.
• New enhancements to Google Search are being added, including better voice searches and the ability to anticipate future questions based on the questions you asked before.