AudioSwitcher

Quick and complete control over all your audio devices used in homes and studios around the world. "Ranked in 20 App Stores around the world!" - AppFigures.com

* El Capitan has broken AirPlay discover read http://goo.gl/g6oHvI

* Please, save yourself a potential headache (and a dollar) and read the FAQs before you buy: http://goo.gl/m3pu7L

For example:
1. You can't change HDMI volume - that's a hardware limitation with HDMI itself, HDMI doesn't carry volume information
2. You can't plug in headphones and switch to internal speakers - that's a hardware limitation with your Mac
3. You can't output to wireless and non wireless and always have them in sync - that's partly software, partly hardware and partly physics.
4. If you've got multiple AirPlay devices Apple have removed the functionality to play them all at once or individually since OS X 10.9

Read this far? So here's what AudioSwitcher can do:

If you've got a problem or a suggestion please contact me at feedback@serialangels.co.uk and I'll do my best to help. I get back to 70% of people within TWO hours and 95% people within 24. I've no way of contacting you via the App Store if you just leave a review - many if not all of AudioSwitcher's features are direct responses to individual requests.

"There’s no easier or faster way to send the Mac’s audio output to Apple TV and AirPlay..." - Mac360 Review

AudioSwitcher is a menu bar that allows you to switch quickly between all available input and output devices.  In addition you can change the volume of any device without having to change your current input / output.

You can quickly change the sample rate or output to multiple devices at the same time.

Using the preferences screen you can choose to ignore certain devices, set a default start-up input or output device as well as it’s volume.

AudioSwitcher supports any device available to the system: AirPlay, USB, HDMI, Thunderbolt, Bluetooth etc.

AudioSwitcher is ideal if you have multiple sound devices attached to your Mac and want to be able to switch between them without having to use System Preferences.

It’s great for a home theatre set-up allowing selection of default devices (and their volumes) on start-up as well as allowing you to quickly route output to AirPlay devices in one click.