Piping audio between two Macs

Brian, better late than never (?) but you can use the built-in AUNetSend and AUNetRecieve to do what you want. You can use this with or without Soundflower. Using Soundflower:

On the sending Mac

1. Set System Audio to the desired Soundflower instance (2 channel?) (System Preferences -> Audio -> Output). Alternately, you can use Audio MIDI Setup to create an "Multi-Output Device". This way you can output to (wait for it) multiple output devices, such as, say, the sending Mac's speakers and the receiving Mac's speakers, simultaneously.

2. Install and run AU Lab (https://www.apple.com/itunes/mastered-for-itunes/docs/au_lab.zip).

3. Under "FACTORY CONFIGURATIONS", select "Stereo In/Stereo Out", set the "Audio Input Device" to whichever Soundflower device you are using and the "Audio Output Device" to "Built-in Output" (or the Multi-Output Device you created in Audio MIDI Setup). Click "Create Document".

4. In the resulting window, in the "Output 1" column, there should now be an "Effects" dropdown. Set that to "AUNetSend". At the top of the resulting window you can optionally give this Generator a name by clicking the dropdown menu, third from the left. You can also configure a port if you want and/or give your stream a password (if you want the connection to be protected) as well as set audio/quality.Even on WiFi (802.11N) 24 Bit Apple Lossless should steam with no problems.

On the receiving Mac

1. Again run AU Lab

2. Under "FACTORY CONFIGURATIONS", select "Stereo In/Stereo Out", set the input to None and the output to "Built-in Output" (or again, you can use Audio MIDI Setup on the receiving machine to create an "Multi-Output Device" if for some reason you want to send the audio to multiple devices, say, headphones, a Thunderbolt audio card, and a USB sound card). Click "Create Document".

3. Go to the “Edit” menu (as in menu bar) and select Add Audio Unit Generator. Select "AUNetRecieve"

4. In the Directory pane of the new window, the share name you created earlier should appear. Select it and press "Select Host" and then click the "Connect" button (top right). The "Sender" field should change to reflect the host you just selected, and the “Status” field should change to “Connected”. If all is good, you can close this window. (If you need to edit it later, you do so by selecting the Generator and using Edit -> Edit Selected Generator.)

5. Back at the bottom of the original window, the Generator should say “Audio Engine Running". You can toggle this by clicking.

And there you have it.

Note:

AUNetSend accumulates a bit of lag over the course of several hours. You can fix this as needed by resetting the AUNet connection from either the send or receiving ends. (On the receiver machine, you can do this by selecting the streaming track you made above and then using Edit -> Edit Selected Generator. There you can click the "Disconnect" button which then changes to "Connect". Clicking that will immediately reset the AUNetSend effect plugin and fix the lag. On the sending machine, click the "Effects" drop down menu in the middle of the track you made above, and the AUNetSend window should come up. As with the receiving machine, click the "Disconnect" button and then "Connect".)
Which one you chose depends on how you have the stage set up and which is most convenient but it will sync you back up instantaneously. For a show of a less than a couple hours, though, you should not really experience too much of a sync/lag issue.