HOW TO DO HIGH-PASS & BAND-PASS FILTERING ON AN AKAI WITHOUT THE FILTER BOARD 1) Create an inverted copy of the sample you want to filter. On an s2000 this will require transferring the sample in question off to a computer editor. 2) Place the original sample in one zone of a keygroup and the inverted one in another. It is crucial that they be in the same keygroup as this technique requires phase-coherent playback, which is only gauranteed inside keygroups. 3) Make sure that all of the settings in each of the zones are identical. If all is well, you should not hear anything when you play a note. 4) Set one of the zone's filter offset to +50 and the other's to -50. 5) Now set the filter cutoff for this keygroup to 50. From here, if you modulate the filter downward, it will act like a regular lowpass (since one of the samples is completely filtered out), but if you modulate upwards it will act as a highpass, as one sample will have its filter all the way open and the lower components of the inverse sample will begin to appear as you open its filter, cancelling the lower components of the first sample. A useful way to modulate the filter then, is with a modulation source that can produce both positive and negative values (i.e. a pitchbender or LFO), as opposed to something like the mod-wheel or velocity, which only produce positive values. Try setting a pitch-bender to control the filter. Turn the depth of the bender all the way to +50. Now, when you bend all the way down, you get nothing, and as you raise the bender towards its midpoint, you get a regular lowpass sweep. Raising the bender above its midpoint will introduce the highpass effect, so you can get a morphing filter kind of effect. Another interesting effect is to use LFO2 to control the filter, set to random waveshape with zero rate, so that each note has a random filter (could be highpass or lowpass). Of course, it is also fun to play with the resonance in this situation. One possible effect beyond the typical resonance type things is to crank up the res and then turn the master filter cutoff up a bit. This will cause *2* resonant areas, one at the very top of the range and near the bottom; with a cutoff of about 75 the bottom resonance brings out a lot of booming bass in a loop, while leaving the rest of the loop intact. Of course, the high resonant area will also exist, so be warned that this may bring out any really high frequencies in the sample as well; to offset this, you may want to turn down the zone filter offset of +50 to move this peak to somewhere more agreeable. This brings us to the second point: Band-Pass filters. Band-Pass filters To make a bandpass, set up the patch the same way, but don't turn the filter offsets all the way up to +- 50. This is convenient because you can create bandpasses of arbitrary width; regardless of resonance, simply by tweaking the difference between the filter offsets. Getting this method to sound just right for a given sample or effect may require tweaking the master filter cutoff and then setting the offsets asymmetrically so that you don't have a dea zone at the top/bottom of the frequency range where it stops acting like a bandpass and acts like a highpass/lowpass. also, keep in mind that messing with the resonance will still cause dual peaks, so you can get some wacky bandpass shapes this way. More fun stuff Now that you are bored of playing with the new filters, try messing with the vel>offset parameter in one of the zones. This will throw the sample in question off-phase depending on the velocity you play with, which can result in some funky velocity-dependent bandpass/highpass effects. Also, notice that phase-coherency seems to degrade during the release of the notes (set the filter offsets of the zones back to 00 and the filter cutoff back to 99 and try playing. You should hear nothing until you release the note, then you hear a quiet release). Try using a long release and see what you can get (I don't gaurantee it'll be cool, but you might find something weird). Also, bear in mind that this method will cut into polyphony as you are using two samples for each voice. And please let me know if you find any other cool applications for this. Ethan Duni
