Orbits are indeed the way to go to get separate outputs in Tidal (SuperDirt), but need a little extra config…
Take the “setup with options” example from here: https://github.com/musikinformatik/SuperDirt
For e.g. four stereo outputs you change s.options.numOutputBusChannels = 8; and ~dirt.start(57120, [0, 2, 4, 6]);
The former sets the number of outputs, the latter creates four orbits, the first going to outputs 0 and 1, the second to 2 and 3, and so on. You keep the ~dirt = SuperDirt(2, s); line unchanged because you want each orbit to be stereo.
It’d be great if you can contribute the volca fm synth definition back to tidal-midi! You could send a PR to 0.9-dev branch, and/or join the #tidal channel on the TOPLAP slack if you’d like some help doing that.