Studio One 6's sub-output busses are now also audio recording sources. You can record from any output or sub-output, if you configure routing that doesn't create a feedback loop. To record the master bus mix back to an audio track in real time, follow the steps below.
1. Go Options (Windows)/Preferences (macOS) > Audio Setup.
2. Click the Song Setup button on the bottom of that dialog window.
3. Click Audio I/O Setup and select the Outputs tab.
4. As shown in the image below in the Outputs tab, create a new sub-out by clicking the Add Stereo button at the bottom of that window. Don't click any of the assignment boxes, leave them blank as shown in the image.
5. Click the Make Default button near the bottom so that the dummy output will be part of your default I/O setup for every new song and hit OK and close the dialog.
Recording From The Master Bus
Now that you have a dummy output to assign those kinds of source tracks to, you can record directly from the Master Bus in real time like with tape or like Pro Tools, to any stereo audio track.
1. Create a new stereo audio track.
2. Assign it's output to the None sub-out. This is necessary because Studio One doesn't allow feedback routing, so the only way that the Master out will become available as an input source is if the track output is not assigned to the master bus.
3. Now you can assign the input of a stereo track to the Master Bus in any song by choosing it from the Outputs folder in the input source list.
4. Put the track into record and turn on the monitor button to see the meters and record. You can't monitor that signal directly from that track in this case but use the meters for activity confirmation. The track will record directly from the master bus.
5. To play back that track after recording, change it's input away from Main to None and set it's output to Main. As expressed earlier, Studio One doesn't allow feedback routing so the Main output won't show up for selection in the track destination list until you switch it's input source away from Main.