Finally, I found this video which explains it very good:pin 1, 19 filter in, and modify noise circuit indeed:External Audio passed thru a Korg Poly 800's filterThis is by far easier than building an external filter box. External Audio passed thru a Korg Poly 800's filter I used the audio output from a Roland JX-1, tapped it into the NJM2069 Filter IC chip and triggered the JX-1's voice via the Korg's MIDI out.. thus triggeri... View on www.youtube.com Preview by Yahoo