MIDI signal via GarageBand in Zoom / Manycam

Hi everyone,

I have the following goal, but I don’t know exactly how to realise it:
The aim is to feed the sound signal via MIDI from an electronic organ into my Mac or PC in order to transmit the organ sound “natively” with Zoom. All video and sound inputs are previously connected via ManyCam to a virtual microphone or camera, which can then be selected in Zoom.
My approach was to first get a MIDI-to-USB interface cable in order to connect the organ to the computer in the first place. Now it is (probably) unfortunately the case that a MIDI signal is only recognised by a few special programmes. Zoom or ManyCam are not among them (I couldn’t try it out yet, of course, because I don’t have the corresponding adapter yet. But what I have read so far unfortunately speaks for it). So you would have to put a programme between the organ and Manycam that somehow converts the MIDI signal into a format that Manycam can read. I read somewhere that GarageBand is able to recognise the MIDI signal (input) and send it to different outputs. Can GarageBand do this and can it also output the sound as “computer audio” or system sound (instead of a specific channel)? Manycam is able to pick up the system sound and pass it on to Zoom. If it all worked like that, my plan would actually work, wouldn’t it? Alternatively, it would be great to have a program that converts a MIDI signal into a virtual microphone which I could then select in Manycam…
Does anyone have experience with this or something similar? Thanks for help!

Kind regards from Germany