[Jackaudio] How to play MIDI sounds through Zoom conferencing?

[Kevin Zembower]

Hello, all, newbie here, both to this forum and to music. I'm a first 
year music theory student at my local community college.

I'm searching for a definitive answer to the question, How to play 
sounds from a MIDI controller to the other participants in a Zoom 
video-conference? I've successfully hooked up my Korg microKEY 
controller to my Ubuntu 18.04.5 computer, using qjackctl 0.4.5, qsynth 
0.5.0 and vmpk 0.4.0. I connect the microKEY2 to the qsynth and the 
VMPK. The patchbay is set up with these connections:

Output                       Input
PulseAudio JACK Sink and qsynth connect to system
a2j 2 connected to a2j 2
Midi Through and microKEY2 connected to a2midid

I can hear the synthesized piano in my headphones and see the VMPK keys 
activate. So far, so good.

I'm using Zoom 5.4.9. I tried to follow the instructions at 
https://www.reddit.com/r/linuxaudio/comments/gckoia/midi_to_zoom_skype_etc/. 
I used paprefs to add simultaneous output on all sound cards. In this 
configuration, when I start Zoom and go to Settings and Audio, I cannot 
hear the Test Speaker sound, but can still hear my piano. When I connect 
to a meeting, the other participant can't hear me or the piano, and I 
can't hear them. I don't know what's meant by "open pavucontrol and 
under playback make qsynth output to the null sink. Under recording make 
the videochat application use the monitor of the null sink." These seem 
to be instruction for JACK, not pavucontrol.

I've seen references to Carla, but it doesn't seem to be in my Ubuntu 
repository, and doesn't seem to be created for Ubuntu 18.04.

Can anyone give me an insight to what I'm doing wrong and how to correct 
it? My normal troubleshooting technique of just try every possible 
combination until something works fails at this task; there's just too 
many moving parts.

Thanks so much for your advice and guidance. Let me know if there's a 
more appropriate place to ask this question.

-Kevin