Using the USB and 5-pin ports simultaneously is discussed in the first 7 or so posts at https://www.yamahasynth.com/ask-a-question/modx-midi-transmission/

and it is confusing and complicated. 😉

Personally, I think the simplest thing to do is connect the MODX' MIDI OUT to your Boss Harmonizer, and connect the MODX' MIDI IN to a simple MIDI-USB adapter (like the Yamaha UX16, Roland UM-One, etc.) which you can connect to your iPad using the Apple Camera Connection Kit you already have. Yes, that simple MIDI-USB adapter also includes something to plug into the MIDI OUT jack and you'll have no place left for that to go, but for your purposes, you don't need to connect that part.

Maybe someone will have a different suggestion...

Thanks, AnotherScott. That is a good suggestion (making it all 5-Pin and no USB).

I wish it was possible without the use of a computer (I do have the iPad as a "computer" but don't really know how to do the routing. I might investigate this).

Now, it can get too complicated than I need it to be so will try the extra USB to MIDI cable soon here but got curious by the thread you posted above ...

If I have Cubasis on the iPad, I can do this?

Per BadMister I can (and he did try it) but I want to strictly use Cubasis 2 ONLY as the "router" to get MIDI mirrored out in 5-Pin MIDI OUT. I can have it running in the background (and hope it does not crash). That is all I will use it for. Is that ok? Everything else is Live Set/s of MultiPart performances on the MODX alone as usual/normal.

(Note: Cubasis 2 is cheaper than the USB/MIDI cable in the App Store today, until 7/3/19. lol)

I don't have any experience with cubasis. It does seem like a bit of a headache to have to learn how to use cubasis just to get the MODX to route MIDI out of its MIDI jack. Maybe someone can post exactly what you need to do to just get that one function out of it.

I don't have any experience with Cubasis either - until about 20 minutes ago. Cubasis 2 LE is free. It took longer to download Cubasis (not sure why it was so slow) than to figure out how to use it.

Unfortunately, neither MODX nor Montage are on the list of supported hardware that unlocks the free version. The latest MX or reface keyboards will. Yamaha USB mixers will too. The bluetooth adapter also does this - which I have (MD-BT01). So maybe down the line I can unlock Cubasis 2 LE if I plan on using it for anything that takes more than 1/2 hour or save anything. For now, the 30 min time limit was more than enough for this and no need to save anything here.

I'm using a Montage ... so you see references to "MONTAGE" - adjust to "MODX" as necessary. There's no difference here between the two.

1) First, I cleared all the default tracks that were there upon the first load. Since I'm not familiar with this - I'm not sure how to create an empty project with one click. So I click the "- DELETE" button until all the tracks are gone. Easy enough.
2) Then "+ ADD" a MIDI track.
3) Then touch the 5-pin MIDI din circle icon. This pops up the routing options. For the MIDI input: "All MIDI ports" I changed to "MONTAGE Port 3", "MIDI THRU" (the down arrow) - I clicked to turn it on (blue) so MIDI flows through to the output, "No MIDI output" touch that and change from "None" to "MONTAGE Port 1"
3a) Finer details: MONTAGE Port 3 (the MIDI input) - I changed this from "All" to "Ch 1". This is because the keyboard I connected to Montage's 5-pin MIDI port only transmits on channel 1. I'm only going to see channel 1 messages as inputs.
3b) Finer details: MONTAGE Port 1 (the MIDI output) - I changed this from "Ch 1" to "All". What this does is takes the input messages and sends the same message to all 16 channels. This is more MIDI traffic than you need. There are other ways to do this that conserve MIDI traffic. I'll cover that later.
4) Now MIDI tracks in Cubasis (at least this demo) all FORCE some kind of VSTi attached to the track. By default, it's an "Acoustic Piano". I wish MIDI tracks would have no instrument attached and force you to set that up. So be it. I couldn't find a way to remove the instrument. Instead, I just turned the volume down on the AUDIO output from this instrument so that the VSTi would not play through Montage's audio bus. For this, notice "Stereo Output" is showing "1/2" as the output channel - still under the MIDI routing section. This is telling me the VSTi is going to send audio output to channels 1/2 (digital audio channels). Touch the "Channel" button on the left-hand side (as in "1 Acoustic Piano", "Routing", "Acoustic Piano", "Insert Effects", "Send Effects" ... these buttons). Then move this slider all the way down. You'll see the output near the top of the slider "1/2 -Infinity" showing you've squelched the audio output.

My "MODX" is set to Multi-Channel mode. Playing keys of the MIDI attached keyboard (a single-channel-only output on CH1) will play any Performance and send to all PARTs.

Now, if you want to clean up the amount of MIDI channels you send to, you can do this. Say I just want to send to channels 1-8 which will cover playing any factory Performance:

5) Use the "DUPLC" button to duplicate the MIDI track 7 times. Now I have 8 tracks total.
6) Modify the 1st track and change (press the "Routing" button) MONTAGE Port 1 output from "All" to "Ch 1"
7) Modify the 2nd track and change MONTAGE Port 1 output from "All" to "Ch 2"
.. and so on until the last track
13) Modify the 8th track and change MONTAGE Port 1 output from "All" to "Ch 8"

This will take CH1 as an input and will multiply the messages out to all channels 1-8 feeding back to Montage's tone generator (Port 1).

BTW: on iOS I use something called "MIDI Scope" which shows me the MIDI traffic. I set up a "sideband" MIDI bus from Cubasis to the MIDI Scope channel and was able to verify which MIDI channels setting the output to "All" would cover, for example. You may be able to use such a tool similarly to diagnose MIDI routing issues or get an idea of what's on the bus.

For the MIDI input: "All MIDI ports" I changed to "MONTAGE Port 3", "MIDI THRU" (the down arrow) - I clicked to turn it on (blue) so MIDI flows through to the output, "No MIDI output" touch that and change from "None" to "MONTAGE Port 1"

Keeping in mind that the goal is to take keys played on the Montage/MODX, send them to Cubasis, and have Cubasis send them back out to the Montage/MODX such that the Montage/MODX will echo them back out the MIDI port (to the attached harmonizer), this sounds backwards to me. Shouldn't the MIDI Input be Montage/MODX Port 1 (in order to receive Note On/Off from the Montage/MODX keys) rather than Port 3? Shouldn't the MIDI Output be Montage/MODX Port 3 rather than Port 1 (based on what Bad Mister said in the earlier referenced thread, "Items routed from the computer on 'MODX Port 3' will be passed through the MODX and go OUT the 5-pin jack on the back panel" which is where we want the output to go)?

I was coming back here and going to edit my message to place in connection/goal details. Saw Scott's response, so I'll just add the detail as a new message.

For previous setup ...

Setup:
iPad 9.7 (2017)
Yamaha Montage 7 (MIDI mode = USB). USB 2.0 connected from USB TO HOST port on Montage to Lightning Camera adapter on iPad
Roland RD-2000 (transmit on channel 1 only - simulate "1 zone" keyboards)
Single 5-pin MIDI DIN cable connecting Roland MIDI OUT #1 to Yamaha Montage's MIDI IN

Goal:
With keyboard in MIDI mode, there is no direct connection between the Roland keyboard and Montage's tone generator. I can play Montage keys to make Montage make noise, but playing the Roland keyboard doesn't reach the Montage tone generator. Used iPad to facilitate routing so that Roland piano key note on/off messages were routed from its MIDI bus to the Montage's tone generator MIDI bus. This assumes being able to use the RD-2000 as a "master" controller to Montage as a slave with simultaneous use of Montage for local control.

This may not match what the OP is looking for - there were a lot of similar threads bouncing around. I probably lost sight of the OP's goal when I went to the studio to set this up. Adjust as necessary.

=========

If you want to use Montage as a master controller to the 5-pin MIDI bus then:

Setup:
iPad 9.7 (2017)
Yamaha Montage 7 (MIDI mode = USB). USB 2.0 connected from USB TO HOST port on Montage to Lightning Camera adapter on iPad
Some MIDI device (receive on some configured MIDI channel - CHANNEL X )
Single 5-pin MIDI DIN cable connecting Some MIDI device's MIDI IN port to Yamaha Montage's MIDI OUT

Goal:
With keyboard in MIDI mode, there is no direct connection between the MIDI device and Montage's MIDI output produced by playing piano keys. I can play Montage keys to make Montage make noise, but playing the Montage keyboard doesn't reach the 5-pin MIDI connected external device. Used iPad to facilitate routing so that Montage piano key note on/off messages were routed from its MIDI bus on USB to the Montage's 5-pin MIDI bus where the external device is connected. This assumes using Montage as a master controller for both local sounds and external DIN connected devices while USB mode is selected.

All the same setup as before except:

3) Then touch the 5-pin MIDI din circle icon. This pops up the routing options. For the MIDI input: "All MIDI ports" I changed to "MONTAGE Port 1", "MIDI THRU" (the down arrow) - I clicked to turn it on (blue) so MIDI flows through to the output, "No MIDI output" touch that and change from "None" to "MONTAGE Port 3"
3a) Finer details: MONTAGE Port 1 (the MIDI input) - depends on goals here. I would probably pick a PART I use for the TC like PART 1 and set this to "Ch 1". This would assume your PART 1 would always have the keyboard range you want for outputting to the TC. You could always use a dedicated PART/channel (like PART/Ch 8).
3b) Finer details: MONTAGE Port 3 (the MIDI output) - I would probably leave this as Ch 1 and setup the TC to CH1. These two have to match.

There is no worry about MIDI bus congestion - so the steps 5-13 do not apply in this case.

Another Cubasis tip: under SETUP, pick "Audio" setup and turn on the background audio button. This doesn't just apply to audio - it applies to MIDI too. Try it out. Keep background audio OFF and switch from Cubasis to the iOS homescreen. You won't hear your routing working anymore. Then set this setup feature ON and do the same thing - you'll hear your routing working even when Cubasis is not active in the foreground. This would be required, in my opinion, on the bandstand because who knows if something would happen and take focus away from Cubasis. This is an insurance policy.

Yes, he's currently using the iPad to manage his set list in real time, so that app needs to be "in front" and cubasis has to do the MIDI routing as a background process. It makes sense that "background audio" has to be on. To conserve power (and possibly to ease processor/memory demands), most apps don't run in the background unless specifically enabled to do so. An option like that is a little misleadingly named, but yeah, you'd have to look for the option that enables background processing, i.e. all background operation of the app, otherwise it suspends. As far as I've seen, it's always an all-or-none thing... either all processing continues when in the background, or it's all suspended.

It may also be possible to split the screen with both sharing. I saw I could do this with my MIDI monitor without having to turn on the background feature in Cubasis. Regardless - even if that worked - I'd turn "background audio" on.

Wow, Jason! This is as complete as I ever expected it. I will try the setup you mentioned

iPad 9.7 (2017)
(except MODX6 here) Yamaha Montage 7 (MIDI mode = USB). USB 2.0 connected from USB TO HOST port on Montage to Lightning Camera adapter on iPad
Some MIDI device (receive on some configured MIDI channel - CHANNEL X )
Single 5-pin MIDI DIN cable connecting Some MIDI device's MIDI IN port to Yamaha Montage's MIDI OUT

8 Cubasis MIDI tracks all with MIDI IN of MODX Port1 (Channel 1-8 respectively) and MIDI OUT of MODX Port3 (Channel 1-8 as well)

Although, I am thinking of making all 8 MIDI OUTs on Port3 set on Channel1 and have MODX 5-Pin MIDI OUT to my Boss MIDI IN (set to receive info in Ch 1).

Will see what happens...

PS: Thanks for the Background Audio tip. I am sure it saved me trouble way ahead of time. 🙂

Thanks, AnotherScott, you are right and thanks for clarifying in my behalf - "...using the iPad to manage his set list in real time..."

No problem. Unless your "full" version of Cubasis has a lot more options than Cubasis LE - there's not a lot to "learn" in Cubasis. There seem to be hardly any settings or options - lots of things are "hard coded" for you unlike Cubase. So it doesn't take all that long to run through the entire program to find options/settings/etc. That's by design. Fits the tag line "Music. Simply Made" from their Cubasis 2 promo video.

Since I have Camelot - I didn't see why I would want Cubasis. I recognize they're not the same feature sets - I use the MIDI side, not the audio side. Still, Camelot supports hosting AUv3 if I wanted to get into that. But Cubasis is currently at the right price to just throw into the bag of tricks. That said - it's difficult to see the difference between the sale and regular price considering each season seems to have this same 50% off sale lately.

As far as using an iPad to connect the two MIDI buses - I think it's good to have the outline of both directions / use cases. There seem to be an equal amount of others trying to get things to work the other way too.