“Overtone GEQ is 7-band harmonic (overtone) graphic equalizer AU and VST plugin with multi-channel operation support (supporting up to 8 input/output channels, host setup-dependent). Overtone GEQ offers extensive internal channel routing capabilities, and supports mid/side channel processing.
Beside equalizing, Overtone GEQ applies harmonic enhancement processing: it uses 7 harmonic enhancement modules, one for each EQ band. This generates a complex harmonic coloration you will probably like a lot.
Overtone GEQ was designed to allow audio engineers to apply quick EQ shape adjustments together with adding a bit of harmonic richness to the audio material (mainly mixes and sub-mixes due to a comparably high processing load this EQ puts on a CPU).”
Source : voxengo.com