… I think your suggestion for custom scales would be much better than the triad/chordal voicings. With custom scales you could just program anything you want. For a device that is called the H90 Harmonizer, I was actually pretty surprised that this is not a part of the Diatonic algo …

I’ve been a proponent of this idea since the PitchFactor days.  I don’t think it’d be out of the realm of possibility in the H90.  The question remains:  How to get the custom scale entered in?  I still say the most painless method would be MIDI Note entry, or playing in a bar or two sequence of MIDI Notes.

… I just want to play Satriani’s ‘Why’….please help me dear Eventide 🙏🏻

Embrace MIDI.  You can probably get there with enough Aux switches; two sets of 3.  I prefer two CCs stacked on a single switch.  Simple, foolproof, repeatable.  For pitch axis “theory” – with a pedal point – one CC message.

https://www.eventideaudio.com/forums/topic/pitchfactor-key-toggling-over-midi/#post-123733