I've been trying to do the same thing for some time now. I know that this is a feature request that has been out there for practically ever.
It is possible to import a single midi file that will start when the patch is played however the only way to stop it is to quit MS. What you would do would be to create an External MIDI channel. Then in the channel strip inspector there is an option for 'Send MIDI File". Check this and then import your MIDI file.
I have had to use Ableton for live performances because it will allow you to import and play a midi track with other backing tracks. You can also set the BPM by adding the value in the title. I would still much rather use MainStage though as we can also connect an iPod to it easily which would allow for changing of vocal and guitar effects that we have previously setup.
Current setup uses a backing track and click track (The latter is routed to the in Ear monitors). We then use a MIDI track to control all of the lights. The MIDI commands are sent to LightKey which holds the various scenes for the lights.
I *believe* that it may be possible to use another DAW or MIDI player in ReWire mode from MainStage, but I have had trouble getting this to work also. When I tried to ReWire Ableton Live 9 to MainStage was when I realized that I could just use Ableton.
Again using Ableton is not ideal for me, but it will work. If *ANYONE* has any other suggestions for importing and playing a MIDI track, please let me know...s
• Logic version and sub-version = Logic 10.2.0
• OS X version and sub-version = OS 10.11
• Computer = MacBook Pro, 17-inch (Early 2009)
• Processor = 2.66 GHz Intel Core 2 Duo
• Memory = 8GB
• Audio interface manufacturer and model = Focusrite Scarlett 18i20