I am using Ableton to build backing tracks for songs - I have several audio tracks and 3 midi tracks; two of them are used for program changes for 2 different keyboards, and one midi track with notes - I see where I could build the program changes in Stage Traxx 3 manually (assigning timeframe) or recording (GREAT!!!). However, I don't see any documentation to where I could import a midi track that contains midi notes to drive my light show on an external light controller?
Playing midi tracks (Notes) along with audio tracks
Implementing a full blown midi player is not on my todo list as it is very complicated to get the audio and midi part to be fully synced especially when using timestretching.
And storage is cheap, I don't really see a reason to use midi playback especially since you can not edit the tracks in ST3 anyway. Just render your midi files as audio and use that.
Keyboard program changes work just fine with the integrated midi system and will be sent at the correct time even when changing song speed.
As for lighting it depends. If you just trigger certain scenes/cues in your lighting software, the integrated system will work fine.