I’ve run into the problem of having most of the sound systems I work with running in mono, and Mainstage working best in stereo. Sure, I could slap a gain plugin and click the mono setting on the master output, but that would mean if I’m running click tracks out through the master bus, it’s going to come through both the left channel and the right. 

I had to do some digging, but I finally figured out the “right” way to run a mono system in Mainstage. Here’s how to do it: 

1. The first step is to setup your built-in metronome correctly. In the channel strip window, select “show metronome channel strip”. 

2. Pan it hard right. 

3. In the channel strip window, select output>change all> bus 1. This will route the signal from everything expect the metronome to bus 1. 

4. On the Bus 1 channel strip, add the audio fx “gain”. 

5. Open up the plug in window, and select “mono”. 

6. Pan the Bus 1 channel strip hard left. 

You should now hear your keyboards out of your left channel (properly summed and ready for live use), and just your metronome in your right channel. 

Note: if you're running tracks, simply put a gain plugin on it and select the mono option, then pan the track hard left.