It\'s resonance for a piano, in a sense. Try experimenting, adding a very little of the effect and tweaking the knobs:

\"...a bank of six comb filters that resonate at a specified pitch. Each filter can take it’s pitch from either a Note name (eg C2), from a typed in frequency (in Hertz) or from the midi input (channels 1-6). There are detune, feedback, damping, pan and volume controls for each comb filter. There is a SV filter before the combs which can make the combs resonate better. A noise oscillator is also included to excite the comb filters. There are lfos for the filter, pan and pitch. There is a delay effect built in and a basic oscillator for reinforcing the drone. A pitch-bend slider can bend all the comb pitches and it can be quantised to move in semitones, tones, fifths or octaves. It can also quantise the pitch lfo.\"

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