If you’re on linux, you can install jack through your favorite package manager, then install svn (subversion) and get Jag’s code and instructions from his project page.

If you’re an OS X version of some sort, please read on.

First, go get JackPilot and Jack: http://www.jackosx.com/download.html (download the version for your version of OS X).  Install it, and restart the computer.  We’ll wait here while you do that…

Next, run JackPilot (from your /Applications folder).

Now we need to set up our sound device.  The odd thing about the Mac laptops is that they have different sound drivers for input and output, which is a pain for Jack to deal with.  We’ll need to create an “Aggregate Device” which smushes together the inputs and outputs into a single, virtual device.  Luckily, this is easy to do.

Open Audio Midi Setup (an application in your Applications/Utilities folder on your Mac) and then we’ll create the aggregate device.  Note that from the JackPilot menu you can also get to your Sound Preferences at the click of a button (we’ll need this soon enough).

In Audio Midi Setup choose “Open Aggregate Device Editor” from the top menu as below:

Next, click the + sign to add a new aggregate device, and make it look the way it does in this screenshot:

Now click “done” and you’ve got a brand new audio device that you can use with Jack. Go grab a coffee, or a biscuit, and pat yourself on the back because we’re almost done.

Close Audio Midi Setup and go back to JackPilot.  Now, choose “Open Sound Preferences” from the top menu that you chose “Open Audio Midi setup” from before.  In Sound Preferences, choose your “Aggregate Device” as your audio output:

Do the same for the input (under the “input” tab).  Now we’re ready to use Jack! One thing to note is that your volume keys won’t work with this Aggregate Device, you’ll need to control all your volume via software.  A pain, I know, but such is life.

Go back to JackPilot and hit the “start” button to start the Jack server.

Now you need to download the handy disk image containing the XCode project file and supporting files.

Open the disk image and copy the files to a safe place on your computer, like the Documents folder.  Double-click the project file.  Oh, make sure that XCode (part of the Developer tools) is installed – if not, you can install it off the OS X disk that came with your computer, or (better yet) download it from Apple’s Developer website (free registration) which will give you a newer version with better support.

Once you have the project open in XCode, go to the top menu and click Run and then Console or press SHIFT+CMD+R.  You should see the a console window pop-up, where you can type in commands and get some textual feedback from the program.  Now click the “Build and Go” button on the top bar of any window, which has a little green play arrow, and the program should run (you’ll see some text in the console window).

We need to connect our jack-tuner program to Jack, now, so go back to JackPilot and hit the “routing” button.  you’ll see a window of connections pop up, like so:

Click on the “out” under jack-tuner (our client) and then double-click “playback_1″ under “System” as above to make a connection.  (Double-click it again to break the connection.)  Now you should hear some sound!  Go back to XCode and type in commands into the Console and play with your tuner!