~Of course!
…
And your to-do list should have much better stuff on it than this, haha. 
Thanks though. 
I chose to use dsp_run for simplicity in this case. -Same for copy_vector as nothing more complicated seemed necessary. They seem to work as intended. 
For me, I think these names will do… at least for the time being:
“Channels: 2 → 4”
ardour {
["type"] = "dsp",
name = "Channels: 2 → 4",
category = "Utility",
license = "N/A",
author = "J.K.Lookinland",
description = [[Duplicate stereo inputs to quad outputs, i.e.:
Inputs 1/2 -> Outputs 1/2 and 3/4]]
}
function dsp_ioconfig ()
return {
connect_all_audio_outputs = true,
{ audio_in = 2, audio_out = 4 }
}
end
function dsp_run (ins, outs, n_samples)
-- Route inputs 1/2 -> outputs 1/2 and 3/4:
ARDOUR.DSP.copy_vector(outs[1], ins[1], n_samples)
ARDOUR.DSP.copy_vector(outs[2], ins[2], n_samples)
ARDOUR.DSP.copy_vector(outs[3], ins[1], n_samples)
ARDOUR.DSP.copy_vector(outs[4], ins[2], n_samples)
end
“Channels: 4 → 2”
ardour {
["type"] = "dsp",
name = "Channels: 4 → 2",
category = "Utility",
license = "N/A",
author = "J.K.Lookinland",
description = [[Sum quad inputs back to stereo, i.e.:
Inputs 1/2 and 3/4 -> Outputs 1/2]]
}
function dsp_ioconfig ()
return {
connect_all_audio_outputs = true,
{ audio_in = 4, audio_out = 2 }
}
end
function dsp_run (ins, outs, n_samples)
-- Start with routing inputs 1 and 2:
ARDOUR.DSP.copy_vector(outs[1], ins[1], n_samples)
ARDOUR.DSP.copy_vector(outs[2], ins[2], n_samples)
-- Mix-in inputs 3 and 4 to the outputs:
ARDOUR.DSP.mix_buffers_no_gain(outs[1], ins[3], n_samples)
ARDOUR.DSP.mix_buffers_no_gain(outs[2], ins[4], n_samples)
end
Obviously with the latter script summing identical stereo pairs will result in a +6db boost. So this is really only made for other, mixing trickery, e.g. (in my case) splitting a stereo pair into the more-true mid/shared content, and the more-true side/unique content, editing them separately how you will, then summing them back together.
~Lots of experimentation with routing/pin-connections this week which is fun… 
-J
But something like RJ Studio’s 
