If you use a Mac and don't already use Alfred then download it now. Seriously, stop reading this and download it now :). A Mac without it is unusable for me. This is especially true since the release of Version 2 with the Powerpack add on.
At its core, Alfred is an application launcher that replaces OS X's Spotlight. It has come after earlier generations of similar products including Quicksilver and Butler among others. However, Alfred is much more than an app launcher. A lot of the power comes from the Powerpack add on ( £15) which allows to create complex workflows (which can be download from the Alfred community).
Below is a screenshot from Alfred and the hotkeys I've set. I'm now able to use hotkeys to go to previous/next and play/pause system wide. I don't have Google Play Music as the active tab in Chrome or even have Chrome as the active app. Also with Google's Notification Center (requires Chrome 29 beta) you'll get the nice system wide track info alerts as well (screenshot below).