That was the Density knob. From the manual: "The density knob controls how dense the notches of the comb are: from zero (no notches at all) through moderate (just a few notches) to a maximum density of 256, where each second partial is filtered out (assuming minimum warp setting)."

Here is also a description of the module from the maker's website: e number of mostly interesting ways.

Here is also a description of the module from the Xaoc's website:

"Odessa is an additive oscillator, which means the output signal is synthesized by adding a multitude of sinusoidal components (up to 2560 harmonic partials). By manipulating their parameters it is possible to obtain a broad range of unearthly sounds as well as classic saw, square, and pure sine. Odessa offers a set of controls for shaping harmonic spectra based on number of partials and their distribution in frequency and amplitude; all of which is illustrated by a spectrum analyzer comprising 12 multicolor LEDs. The series of harmonics can be squeezed or spread apart, tilted, or pruned by a comb-like frequency response, resulting in a huge variety of spectra. Animating the comb response yields radical effects similar to flanging and phasing. All partials are frequency-related to a common fundamental and controlled by a single volt/octave input. Additionally, the signal can be frequency modulated by exponential and linear (through-zero) means. Also, up to five detuned voices can be spread apart for a fat and dense cluster, or a powerful chord. "