I'm going to have to plead myself stumped once more I'm afraid. I really like the concept of MIDI routing without using Audio/MIDI setup, and MidiPatchbay is easy enough to use, but the patch is still not connecting as I had expected it to (somebody only barely understands the basics of computer science if claiming so isn't hubris on my part). My process is as follows:

1. Start MIDIPatchbay, create a single universal MIDI strip with both input and output - name "PD-Input"/"PD-Output" for reference. Allows all notes, allows all messages, clocks in real-time.

2. The patch itself doesn't show up in Audio/MIDI setup. That's fine, as I understand it the MIDI signal is traveling through MIDIPatchbay anyways. IAC is turned off and no software instruments are installed. I can close down Audio/MIDI setup and ignore it.

3. Start Mainstage, make sure that the volume is up, a patch is readied, and that Mainstage recognizes that there is a MIDI input available. Mainstage recognizes "1 MIDI input available"

4. Start PD-Extended and open the Sequencer patch.

5. Go through the process of making sure all components of the patch are functioning (it has a sequence tempo set, all the notes are active, volume is up, all the usual goodies).

6. Check DSP to on (I don't think it's necessary, but I tend to idiot proof my processes).

7. Set MIDI output from PD-Extended to "PD-Input" from MIDIPatchbay.

At this point I have all three pieces of software running, I believe in the correct order, and connected to one another with the only glitch being that I don't get a lick of audio. I'll dump the patch here for reference:

MIDI Sequencer Array.pd

I try to keep things fairly self-explanatory in terms of sends/receives and with comments within the object arrangement, but here's hoping it's legible. If the problem is in the coding of the patch I can take it across to that section of the forum. That said, even making a simple patch to create a note with set number, velocity, and duration on manual bang and send through the midiout doesn't seem to be arriving to Mainstage. I suppose I could use one of my other programs capable of MIDI synthesis, but that seems superfluous.

I really appreciate the help, I've worked with PD less frequently over the past five years or so than when I was first learning the ropes; it always seems like I have to re-learn a few things as well as double check on my knowledge of possible objects to use... Always something new.

Putting together a simple sequencer program to interface with synth software across IAC via MIDI. Only, for some reason I don't have the option of using the IAC driver as output from PD. I went through Audio/MIDI setup and made sure that IAC is online and has an open port still no dice. Running a 2015 MacPro with El Capitan OSX 12.

Now I do get an odd error message in the PD Console that suggests that it can't find darwin along with an enormous file address (can't fully fit in the console). I haven't been having too much trouble with it despite this issue. Ought I to consider doing a full re-install of the latest version of PD (as I've updated within the past year), or might I have some other sort of glitch going on?