@ant
The SQ MIDI Protocol document can be found here – https://www.allen-heath.com/media/SQ-MIDI-Protocol-Issue3.pdf
You’ll notice that control options for the mixer include mutes, assignments (to mixes), send levels (all inputs to all outputs), panning/balance and SoftKeys.
There is no control of parameters other than through the SoftKeys, as anything that can be assigned to a SoftKey can be controlled ‘by proxy’.
The messages used are NRPN, which you can automate using Logic, but it may be easier to send CC messages to something like Bome’s MIDI Translator ( https://www.bome.com/products/miditranslator ) which can then send the correct NRPN messages onto the mixer.
If you need a hand with this, please contact us using https://support.allen-heath.com
One other thing I’d note is that with either the stereo tap delay or bucket brigade delays, ‘darkening’ the repeats is controlled by the feedback filter (and the echo is already pretty dark, being a model of a tape delay!)
Thanks!
Keith.