Change volume of airport using the master keys, not itunes volume slider

My roommate recently bought an airport express, and I love it. Minus the fact that when I'm blasting music and someone wants to talk to me, I need to open iTunes and either lower the volume or pause the song.

I am so used to usng the f11 f12 keys that this is driving me insane!

I read somewhere about sizzling keys and how it can help me assign a different shortcut to control iTunes volume. Is there a different, or better, fix?

I would love to be able to use f10-12, and not the iTunes volume.

Note: I am on a Macbook Pro 2012 with standard keyboard, so currently, f10 is mute, f11 lower, f12 raise volume. They work fine when I'm not using airport.

SOLUTION github.com/alberti42/iTunes-Volume-Control

This created assigned cmd - volume key to iTunes so I can control the iTunes volume with very little effort!

This might do what you wanted, however I did not test it my self.

https://github.com/alberti42/iTunes-Volume-Control

I was wondering how Apple could possibly have missed such an obvious thing. All of these answers miss the mark by a bit. Turns out there's a super straightforward answer. System Preferences -> Sound -> Output tab -> Select a device for sound output -> switch it to Airport Express (presuming you're connected to your Airport Express). Now the whole system sound output will be Airport Express and you can use the volume (and mute) buttons as usual with no tricks or sketchy/buggy third-party apps. Moreover, this will now output all your sound, so for example also from YouTube, etc.

I believe system sound effects can be chosen to go through a separate device too, which is nice--click the Sound Effects tab -> Play sound effects through.

Moreover, if you want to switch back & forth between Airport Express and speakers as output device, tick "Show volume in menu bar" at the bottom of sound preferences. This puts a volume icon in your right hand menu bar. OPTION-click on it lets you quickly switch output devices.

1. Open the "Keyboard" System Preferences ("Keyboard" from spotlight)

2. Click on the "Shortcuts" tab.

3. Click on "App Shortcuts" in the bottom of the list on the left.

4. Click the "+" below the list on the right and add the following shortcuts:

   a. iTunes, Increase Volume, fn+command+F12 (or whatever you want)

   b. iTunes, Decrease Volume, fn+command+F11 (or whatever you want)

5. When you are finished you should have preferences configured like this:

Unfortunately, I don't think iTunes has a menu item for "Mute" so you can't use this trick for the mute button. You also apparently need to include fn in your key binding. If those are problems for you, check out the apps suggested in the other answers. But this is a nice, free, solution.