The LxD music synthesizer module, Low Strike Duo, is a dual-response, two channel, direct-coupled, Low Pass Gate, which utilizes vactrols in order to provide simultaneous control over the Amplitude and Frequency Spectrum of an INput Signal. It is, in essence, a VCFA (Voltage Controlled Filter Amplifier). Unlike the Optomix, the LxD offers two different filter responses. CH. 1 offers a 12db/Octave response that is mildly-resonant, while CH. 2 offers a 6db/Octave that is non-resonant. The OUTput of CH. 1 is normalled to the INput of CH. 2. This normalization puts the two channels in series, which is similar to the VCF into VCA arrangement made popular by many monosynths of the 1970s.