Same as resonance, but used to specify the resonance for the second filter. When used, there are two filters applied to the region in series.
resonance2=1.5 resonance2=9 resonance2_oncc100=3
This could be used to have both a high-pass and a low-pass filter, like this:
cutoff=1200 resonance=6 fil2_type=hpf_2p cutoff2=250 resonance2=3