An app for OS X that lives in your menu bar and lets you easily control iTunes or Spotify, without interrupting your workflow.
First, you'll need Xcode. You can download this at the Mac App Store.
Now, use Git to clone the repository and clone the submodules.
git clone https://github.com/mborgerson/TrayPlay.git
cd TrayPlay
git submodule init
git submodule update
Finally, open up the TrayPlay Xcode project. Set the "Scheme" to build the TrayPlay target for "My Mac". Then Product > Run (or the shortcut ⌘R).