Any suggestions on how to add a resonant filter to a keyboard that does not have one?

I have a Alesis Quadrasynth (QS4) and want to do midi-triggered filter sweeps in real-time.

Thank you!


  • Could you provide more information about your setup? What DAW? Any available audio inputs on your audio interface? Do you already have filter plugins?
    – EMV
    Commented Apr 8, 2015 at 12:27
  • Thanks for commenting, I just started using Ubuntu Studio (calfJACK Host looks promising), but much of the software options are new to me. I have been using PC with Windows XP with Line6 TonePort & Sound Blaster Live! Drive, Sonar (1st version), Anvil, Caustic3, MidiOx, MidiYoke, and Sound Forge. Keyboard is Quadrasynth. I also have a MMT-8 sequencer. Commented Apr 9, 2015 at 3:27
  • I have not used any filter plugins. Both sound cards have audio inputs, keyboard has 2 main outs and 2 auxillary outs. Commented Apr 9, 2015 at 3:30
  • My version of Sonar can only use DirectX plugins. I am open to trying a new DAW and am looking at Ardour3. Commented Apr 9, 2015 at 3:32

2 Answers 2


there is a free vst called north pole that can follow the envelope of the audio through it



I have heard wonderful things about this box: http://www.sherman.be/index.php/products/filterbank

If you are comfortable with circuits (or learning) it wouldn't be especially hard to build your own midi-controllable filter with an Arduino. The schematics of a moog ladder filter are widely available.

You can try looking at a Guitar FX pedal as well.

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