I recently updated my LFM + PM test patches with the addition of Neóni as well as several other changes. One of those changes was the addition of a short melody being played into the oscillators’ V/OCT inputs.
I bring this up because this led me to find something interesting: there are 3 TZLFM oscillators included in the FM patch (Chebyshev is missing because it lacks a sync input), but Terrorform (with hard-sync) stands apart in that it is the only one that holds the melody rock-steady while using hard sync.
(However Neóni-with-hard-sync and Terrorform-with-soft-sync do something else interesting and musical; they do hold the melody but also rhythmically oscillate down a major third. The rhythm comes as part of the algorithm sequence that I’m using, and the pitch comes from one of the 4 main oscillators involved in the configuration I’m using.)
I’m really curious about what Valley is doing differently here to make this happen. Looking at your investigation here, both Fundamental WT VCO and Terrorform use a constant Hz/volt so that’s not it. Given that Terrorform-with-soft-sync acts more like Neóni-with-hard-sync, I’d guess that it’s something related to the implementation of sync but that’s just a guess. It’s odd that the similarities seen between Neóni and Terrorform are reversed in terms of sync.