No surprise, Google Music is getting deep Google+ integration. For any songs that you purchase, you'll be able to share with friends or circles on Google+. In order to help drive additional purchases, Google will let any friends that you share with listen to the entire song, instead of the initial 90 seconds, for free. From within the Google Music interface, simply click the down arrow near the end of each song title, select share, and a Google+ overlay will appear on screen for sharing with your friends or circles. It's similar to Apple's Ping, but hooked into Google's own social network.