This is probably common knowledge.
Google play music works on Raspbian Chromium.
Just log into your account and stream. The website has full html5 support in Chromium. Plus you can download and upload your music (not recommends as it's slow).
Try it out in Chromium here:
It uses around 400mb ram on Raspberry Pi 2B 1.1. And initially it takes around 20 seconds to boot up the site. Once it's up and running it will play music smoothly.
If you have any tips share them below.