If you’re using an expression pedal with MainStage, it’s usually mapped to MIDI CC#11, which controls a channel strip’s expression dial. While this method technically works, it’s not the ideal way to control volume in MainStage. The proper way to use an expression pedal is to map it to control your concert’s main outputs with a range of -∞ dB to 0 dB.
But what if you find yourself in a situation where you only want to control the volume of a single channel strip in a patch? By mapping the expression pedal to control various auxiliary buses, you can selectively apply volume control to different elements of a patch.
In the screenshot below, I have a patch containing two channel strips — Electric Piano and Strings. As you can see, expression control has been filtered out, thereby locking the channel strip’s expression dial at 127.