When we talk about Chorus and the Flanger effects in CORVEX, we don't only refer to one of the two effects, but also the variations between them which go beyond standard concepts.

A chorus generates the typical 'floating' sound as known from guitar sounds or synthesizer pads. You can add acoustic 'depth' to an instrument to add more power to the sound or to create the illusion that it exists multiple times.

The Chorus sound is created by using the so-called Doppler effect. You've probably noticed this phenomenon in daily life: The sound of an approaching ambulance sounds higher than when it is moving away. This effect is a result of the speed of the sound which first increases and then decreases, thus also changing the sound pitch. If there were a second siren at your location, an oscillation would develop between both sounds (just like when two instruments are out of tune).

Chorus also splits the signal into at least two: a direct sound and an effects part, whereby we have multiple effects parts in CORVEX.

The Doppler effect is created by a short signal delay from the effect. For most equipment this delay is within the range of 10-30 ms (as in this one), this means that it is too short to be perceived as an "echo". The times would also be similarly short if you were to double a guitar track for instance. An ordinary short delay in the mix already sounds "doubled" but is not authentic. This is where the above-mentioned "out-of-tune" effect comes in: the pitch of the effect signal is slightly modulated by gently "drifting" forward and backward as a function of the delay time shift. The result is a floating effect where the speed is influenced by drifting.

The "Flange" effect is similar to that of the chorus, but does have a different technical and historical background. It came about by chance: Someone (various sources say John Lennon) slowed down one of two running interconnected tape machines in a studio with his hand. The result, a rather brief delay of the second signal compared to the first, brought about cancellations within the frequency spectrum, leading to a so-called comb filter effect (the sum of both signals creates "peaks" and "dips" in the spectrum that look familiar to the teeth of a comb).

Flanging is basically a chorus effect which, however, has a low delay time (less than 10 ms). 'Release' or doubling of signals is not at the fore in this case; resulting in a far more creative deformation of the frequency response.
A complete flange effect will definitely require feedback: the flange portion is returned to the input to increase the effect. People often talk of the "Jet effect" as it resembles a jet on take-off.