Speculum Free Comb Filter

Speculum Free is a modulation tool capable of operating as a comb filter or as a standard delay effect. The only difference between the two operating modes is in the scaling of the Delay Time parameter. Its range is between 0s and 0.02s while in Comb Filter mode, whereas the maximum value is increased to two seconds while in Delay mode. Obviously, the developer’s idea was to allow for more precise adjustments when using the plugin as a comb filter, as even the smallest of delay time shifts will result in a different sounding timbre.

The plugin also features a built-in low-pass filter with cutoff and resonance controls. The filter is placed outside of the feedback path, so it only affects the signal before it reaches the delay stage. In other words, the feedback signal is not affected by the filter. As a result, the effect is easier to control when working with longer feedback times (to prevent resonance buildups and excess volume) but also somewhat limited as a creative sound design tool. That said, Speculum Free can cover a range of effects, from basic delay and comb filtering to flanging, phasing, and more.

https://www.decadebridge.com/category/software/plugins/

Brandulator

the new free plugin «Brandulator» of its own design that creates a special audio effect with a unique sound that is similar to the flanger, vocoder and the harmonizer, but has a different operating principle, in which the input signal is branched into three channels is adapted comb filters, tone their settings can be changed to 16th times per bar.
The effect also functions as a kind of arpeggiator that operates synchronously with the DAW, so the detailed design should have an appropriate time signature, although it is not required. Tonal settings of each channel can be set either manually using the controls, and accident in accordance with a predetermined harmonic law selected from the list, numbering about three hundred different harmonies. Randomization of tones can be performed either manually or automatically at the beginning of each bar 1,2,3..8.

http://www.kvraudio.com/forum/viewtopic.php?f=6&t=471245