I have a suggestion regarding scale-based harmony effects as the Twin Harmony.
There's a lack in producing triad centered voicings / harmonies like Brian May for instance uses so often in Queen songs as 'Killer Queen', 'Born to love you'.
But also multi-voice-solos of many other guitarists are triad-centered instead of always shifting the same interval.
If I put for instance
Key: C
Scale: Major
Voice: 3rd
and play following notes:
C, D, E, F
then the produced shifts are
E, F, G, A.
So far so good.
But if I play now a G (as 5rd in context of a C-major chord) then it produces me a B which is out of context (unless we are in a Cmaj7).
Correct in this case would be a C instead of a B.
The Digitec HarmonyMan (discontinued product) solved this Triad-Centered voicing problem very efficiently with a simple mapping,
see first table https://www.manualslib.com/manual/380763/Digitech-Harmonyman.html#page=21-manual
LL stands for -6th (-5th on pos/row 5)
L stands for -3rd (-4th on pos/row 1)
H stands for +3rd (+4th on pos/row 5)
HH stands for +6th (+5th on pos/row 1)
It would be very helpful if Line6 could implement something like this in a future firmware of the Helix, thanks!