That's an extremely useful feature in the EHX Ring Thing. It's been feature-requested here before. The closest that you can get in the current ET algorithm is to set up aux switches, an expression pedal, or MIDI for the base pitches.
Both devices rely on manually keying them in with some tap-dancing. But it's a single switch auto-detecting the pitch in the EHX. It seems like the Eventide technology for this is already there in the Diatonic / QuadraVox algorithms.
