The biquad˜ MSP object implements a general second-order IIR digital filter.
The filtergraph˜ object can be used to graphically design a filter response and output the resulting filter coefficients as a list to the biquad˜ object.
The filtergraph˜ object has a variety of operating modes and inlet parameters ... see the help window for more details.
The spectroscope˜ object provides a frequency-domain spectrogram or sonogram display.
The zplane˜ object provides a pole-zero display for filter design.
A few other filter objects in MSP include onepole˜, lowres˜, comb˜ and teeth˜.