I’ve always been annoyed with the way Live disappears the MIDI out menu of a track the instant you drop in an audio effect or instrument. It makes it difficult to route Reaktor’s awesome Spiral instrument, for example, to another instrument track. Or to send LFO controllers from Reaktor to an instrument. You can do it by selecting the Reaktor track as the MIDI in on the destination, but then you lose the ability to also control the instrument from a keyboard or control surface.
Farting around this evening I noticed that you can kludge around this limitation by creating a dummy MIDI track as a MIDI bus:
Notice that the MIDI Bus track has its inputs set to the Reaktor5 track, but also to the Reaktor5 instrument in that track. The MIDI Bus track has its output set to the next track, which has an instrument rack. That doesn’t tie up the MIDI from dropdown in the instrument rack’s track, so the track still accepts note and control information from a control surface or keyboard, or what have you.
The other important point is to set monitor to “In” for your two target tracks.
Maybe this is a well known workaround now but a year or two ago when I googled for solutions I found only complaints and no fixes. I hope this helps somebody else because it sure opens up possibilities for me!