This is the most informed post that I’ve seen on the INTENSITY control [from Russ Wedelich – Eventide]:
https://www.eventideaudio.com/comment/20065#comment-20065
Dan Gillespie – Eventide describes INTENSITY as controlling feedback in the Phaser / Flanger algorithms:
https://www.eventideaudio.com/comment/12049#comment-12049
It’s worth mentioning that the new per-preset WET / DRY routings can separate your input & processed signals; irregardless of the current INTENSITY value. You will need an external device – or multiple amps – to remix them to subtle proportions, though. But there may be another option open to you.
When I need similar effects mixed to the far background (and I’ve been doing that much more here lately), I’ve been turning to the Delay and Pitch algorithms. Many of them have a MIX or WET MIX control, some type of modulation, short delays, and feedback routings. You can dial in just a hint of phase, filter, and flanging FX.
Here are a half-dozen examples of that concept:
