One or two examples for a sort of harmonic tremolo would be nice, I can’t get the sound…

For the Vibrato algorithm, you may check out those factory presets in H9 Control. 

For the Harmodulator algorithm, you need to set the Pitch A and B to Unison, set the Mod Depth to a small value (like 30c or m2), and Shape parameter to SINE or TRIANGLE, then you should be able to get some harmonic tremolo sound.

The Harmodulator settings sounds like the micropitch algo. The vibrato settings sounds very univiby, but not like a harmonic tremolo at all. So it could be a nice new and very usable algo, or an addition to a univibe algo (if Eventide is working on it…)  🙂