This is the bandpass filter that had its own signal path from the sawtooth output of a GX1 voice's VCO to select specific harmonics from the waveform. In the GX1 this resonator had a fixed Q of 5 but this has been made variable (0.5 to 15) in the module. This was a "side chain" signal path to the primary GX1 voice that uses the NE10400/10500 filters (which I turned into the MOTM-485) that the Electone design team--organ builders, remember--used for enhancing various reed, brass and string voicings remade as a standard 1U x 5U module. Has power connectors for both MOTM and synthesizers.com power cables. Note: mounting screws and power cable not included.