The Modor NF-1 has been a very popular synth, we really enjoyed it when we got one for review some time back... The Comb Filter prototype that we saw at this years Superbooth is a stereo eurorack version from the NF-1.
Comb filters are implemented by adding a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced notches, giving the appearance of a comb. You can get a number of different effects from a Comb filter and it not something that you see very often in the eurorack world.
More info at Modor Music
Developments for Korg's instrument have been slow but promising.
The Avila Brothers talk about their journey to the recent Super Bowl Halftime Show