rj_filter2
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This is an audio-range filter module with 30 different low-pass filter configurations based on different arrangements of up to 5 filter stages, including many which model analog component variations, based on the Stilsen/Smith Moog design with Q compensation, and several high-pass filters. 

The Input pin is the audio signal from the Oscillator or other well behaved
signal. (If the signal is not within the normal range, there may be clipping.)

The Output pin is the filtered signal.

The Frequency pin is the cutoff frequency of the filter. This more or less follows the 1V per 8ve rule for synthedit

The Resonance pin controls the resonance from 0 to  10. Typically self resonance will occur around 9V input, but each filter's response is different.

The Zing pin adjusts how much resonance changes depending on the frequency pin from 5 to 15. 10v is typical for flat response, but each filter's response is different. (Note that in general, the cutoff rate in db/8ve decreases as the frequency rises in this filter's design, and the Zing pin helps this kid of interesting variation.)

The Type pin select high pass or low pass. Not every low pass filter has a high pass equivalent, they are provided as a bonus: use your ears.

The Poles pin selects the different filter configurations. 

  * The configurations with an "f" are fast versions which do not model analog component variation; the components without an "f" model the .5-5% variations in values of the discrete resistors and capacitors of old real analog components and may be quite CPU intensive. Consequently they may be better suited for monophonic mode syths. The modes which do not have an "f" are designed to distort well: users may prefer to drive over the customary levels.

  * The configurations are typically named using two numbers divided by a ":". The first number represents how many filter stages (called "poles" probably innaccurately) the signal goes through before it is sent to the output. The second number represents how many stages the signal goes through before it is fed back into resonance. So "4:4 pole" is nominally more like a Moog 24db/8ve filter, while "2:2 pole" is nominally more like an Oberheim 12 db/8ve filter. (To my ear, however, the "4:5" and "2:3" filters do better emulations.)

 * There are a few configurations where before the ":" are two numbers separated by the minus sign "-". In these cases, the number after the "-" represents one or more small high-pass stage added, which makes the filter like a lop-sided band-pass filter. So "4-1:5f" means that the output signal is the result of four low pass stages and one high pass stage, and that the resonance is based on 5 stages. 

Due to the different responses of each filter, and the large number of them, 
and the extra effort required to explain to users what is going on,
developers might prefer to pick three or four of their favorites, give them
qualitative names ("creamy", "bright", etc) rather than just expose the pins
directly. 

Available for unrestricted use. No warranty of quality or fitness for purpose
made. No promise of maintenance. Please include an acknowledgement to me (Rick Jelliffe) in the GUI, docs or website, as appropriate (however this is not a condition of use, just politeness and so I can track usage).

Copy it into Modules/MyModules