Take advantage of every AirPlay output and play tunes around your home, in sync.
Including your favorite music player. Easily AirPlay Spotify, Pandora, Rdio, SoundCloud, Grooveshark, Simfy, Deezer. Really anything.
Porthole provides an easy way to control multiple devices using the Porthole Speaker Panel.
Porthole works on post 2007 Macs running Snow Leopard, Lion, Mountain Lion, Mavericks, Yosemite and El Capitan.
Localized for:

Porthole's main goals are to be elegant and make AirPlaying Spotify and other music services as easy as it should be.
Need help? Follow the Quick Start Guide or contact support.
Play through your Mac's output while you're streaming. All the wireless receivers and your Mac will even play in sync!
Syncing is supported by the AirPort Express, Apple TV, licensed speakers and receivers and a number of apps. Download the trial to test your setup.
Use the volume keys on your keyboard to alter the main AirPlay volume. Even the mute button just works.
Think some of your speakers are a little too loud or too soft? Adjust their output by going into Preferences → Volume.
New years eve was a great success. Fuelled by @getporthole multi room @Spotify, great app for syncronising AirPlay.
— Will Beardmore (@willbeardmore) January 1, 2015
My @Spotify and @getporthole setup is super awesome. Streaming songs straight off the internetz into any room in my house. Indie everywhere!
— Rob Whittaker (@purinkle) June 21, 2014
While you can stream your iTunes audio over AirPlay – that’s it. Pandora, Rdio, Spotify, or users of any other audio app are out of luck. That’s where Porthole comes in, it’s a nifty little utility that lets you stream all of your Mac’s audio over AirPlay.
— Alex Arena (appstorm.net)
Porthole adds an item to your menu bar that transfers your system audio to an AirPort Express with one click. It's a piece of cake.
— Adam Pash (lifehacker.com)
Adjust your speaker settings or the volume away from your Mac by using the convenient remote control. Don't get up from your couch to manage Porthole!
The remote works with both the trial and full version of Porthole. Separate $0,99 purchase through Unified Remote. Read more...
Start or stop streaming without taking your mind off what you're doing by toggling speakers with the press of a button.
Use Porthole's hotkey activated Speaker Panel to manage your setup, sans mouse.
Use AppleScript (and JavaScript in Yosemite) to toggle speakers on or off and implement all kinds of cool tricks.
Read the Scripting Tutorial to get started.