MIDI re-routing from one app to another

[macstatic]

How do I re-route MIDI output from one app (a sequencer) over to Logic Pro, so that Logic is basically used as a software instrument?

Trying to troubleshoot I've been monitoring the MIDI signals using the MIDI Monitor app while the sequencing is playing a never ending (looping) sequence. And indeed, my audio/MIDI interface (Focusrite Scarlett 18i20) is outputting MIDI as seen here:

But I'm still not getting Logic Pro to receive that MIDI data to play a software instrument there.
So since I'm far from being "fluent" in using Logic I decided to simplify things and run a stand-alone software instrument, but also there I heard nothing. Actually I tried several stand-alone software instruments, and double checked their MIDI setup where I could only select the 18i20 interface.
So this brings me to the Audio MIDI setup app which currently looks like this (following the instructions in the Roland A-Pro USB keyboard's manual). I have a feeling I need to do something with the 18i20 in that setup, but not sure how. Obviously it's not the A-Pro keyboard I want to send the MIDI to, but another app on my Mac.
Suggestions?

 

[macstatic]

Having given it some further thought..... since the MIDI signals come OUT of the "Scarlett 18i20 USB" (audio/MIDI interface) and Logic, Garageband or whatever is expecting MIDI signals to flow IN to the Scarlett 18i20 I suppose the logical answer is to connect the 18i20 OUT to its IN, but I'm not able to do this.
Do I need to create a virtual MIDI connection of some sort to get this working?

 

[jackerin]

A search led me to this page about virtual MIDI ports in Logic: https://support.apple.com/guide/log...vices-overview-logic-pro-mac-lgcpa24ebb64/mac
I haven't tried it myself, having no other MIDI-enabled software other than Garageband...

edit: apparently it's not available in the Mojave-compatible
edit2: found this page detailing a bit more about the IAC driver in the Audio/Midi tool: https://musicrigs.com/mac-virtual-midi

 

[macstatic]

A search led me to this page about virtual MIDI ports in Logic: https://support.apple.com/guide/log...vices-overview-logic-pro-mac-lgcpa24ebb64/mac
I haven't tried it myself, having no other MIDI-enabled software other than Garageband...

edit: apparently it's not available in the Mojave-compatible
edit2: found this page detailing a bit more about the IAC driver in the Audio/Midi tool: https://musicrigs.com/mac-virtual-midi

You're right! Creating a virtual MIDI port was the way to go.
I didn't know that Logic Pro had a feature for this in the app itself, so that's good to know for later.

But for now I managed to solve it using the method with the IAC driver in your 2nd link. Don't ask me why, but I actually got it working by just enabling "Device is online" but without creating an additional virtual output, like this:

After this was done I went to the MIDI settings of the app which was to send the MIDI signals, chosing "IAC driver bus 1" as its OUTPUT.
Then in Logic (or whatever app was to receive the MIDI data, such as a stand-alone synthesizer instrument app) I went to its MIDI settings and chose "IAC driver bus 1" as its INPUT.

The only thing I can't figure out is how to play multiple instruments on different MIDI channels in Logic (i.e. bass on channel 1, piano on channel 2, strings on channel 3 etc.), but I believe that's more of a Logic-related issue than MIDI port routing (and maybe it has to do with what was written in the 1st link you posted).