The tb303 acid box uses them to allow seemingly infinite timbre variety. You've heard an example of one in the world's most ripped .mod sample: the infamous "resonatix" (see spa.mod [space debris]). In fact, they encompass much of synthesized music today. I speak of course of filters. Flange, resonance, modulated frequency equalization; it's all the same. It's a way to add interest to an otherwise plain instrument timbre.
Unfortunately, it's very diffucult to implement the use of a filter in any tracked format; the reason being that there simply is no "filter effect." There is nothing in any tracker that allows you to ask it to take the current sample being played and filter it. You can fake reverb with additional channels and volume changes; you can fake a flange by playing the same sample simultaneously on two channels and modifying the pitch slightly on one or the other; but you simply cannot fake a filter sweep. Or can you?
You have surely seen .mod's with multi-part synths, usually consisting of 3, 5, or 7 samples. The first sounds simple, the next is comprised of more complex wave geometry; the last is most complex, looking like what you'd obtain from a broken oscilloscope, and sounding like it could break windows if played at the right pitch and much volume. Well, this is one primitive example of filtering. Whoever created these samples hooked up an analogue synth to their sound card and played around with certain knobs on the synth, sampling all the while, in an attempt to capture the filtering effect. Unfortunately, the end result is quite crude; quantized to a fault. You'd have to take many more samples to capture the effect. This proves impractical, as you end up with multiple copies of what is, essentially, the same instrument.
Another primitive form of capturing an analogue effect is sampling a pad synth that's being filtered, dumping the result to one very long sample. However, we still have the same problem of increasingly huge modules; not to mention that the sample has no tie to the rhythm of your tune. Studio composers will often try to match the progression of filter usage to the song rhythm. If you play with synthesizer parameters arbitrarily while sampling, there is absolutely no guarauntee that the effect will synchronize; even less so if you just rip such samples from other modules.
So what are we to do?
I don't know. (Wait around for those coder-phreaks in Cubic Team to put their Fast Fourier Transforms to good use and implement real-time filters in a tracker? =)
But I have discovered a particularly neat thing you can do with a filtered key-hit synth, some creative volume envelopes, and about 30 minutes of spare time. The end result can be quite impressive, given enough effort. (A word of caution at this point: I am partial to Fasttracker II, so what follows may or may not make more sense to users of FT2 than it will to InertiaTracker musicians. Also, users of ScreamTracker3 and Multitracker will not be able to implement the method to its full extent, since neither supports volume envelopes.)
Here's what you do:
Step 1) Acquire a sample. Short key hits are best, but any sample that seems to be the product of analogue filtering, and that has clear and definite peaks and valleys occuring at regular intervals, will work.
Step 2) Deconstruct the sample into some arbitrary number of shorter samples. That number is entirely up to you. It all depends on how accurately you want to be able to reconstruct the filter effect. Take a good look at the sample and approximate how many peaks you see. Let's say you have a sample that has 35 or so clear peaks. That means the sample is probably a sinewave (or other periodic function) that has been filtered over 35 periods. Zoom in and take a closer look. You'll soon notice that each sinusoid is unique, as a result of the filtering. What you want to be able to do is capture the essence of the filter. How do you do this? Quite simply. Copy an arbitrary number of sinusoidal portions, in order, and save them as new samples. In our 35-sinusoid example, we may want to take 9 sub-samples. Save the first, fourth, eighth, twelfth, sixteenth, twentieth, twenty-fourth, twenty-eighth, and thirtieth sinusoid to new samples. For the trigonometrically impaired, here's what you're looking for:
previous -->|<------ target sinusoid ------>|<-- next
| **** | ****
| *** ** | * * *
| * ** | ** *
------*|*------------**---------------*|*----------**----
*| **** *** | **
* ** | ** ** | **
*** | **** | **
Step 3) Edit the sinusoids so that they loop, and loop clean. Clicks are evil. Eliminate them. The easiest way to get a clean loop is to make sure that it begins and ends on the axis. Fade a very small portion of the beginning and end to make sure that they fade in/out to zero, if necessary.
Step 4) Tune your loops. This is the most time consuming and crucial part of the surgical procedure. Leave the first sample as is, and tune the others relative to the first. There's no easy way to do this. Bite the bullet and invest some time. When you think you're done, play around and see if every sample is in tune with every other one. Do some fine tuning if you must.
Step 5) Get creative with volume envelopes. I can only suggest two guidelines. Make your loop sound less like a loop, and more like an instrument. Make provisions for some form of sustain, either using a post-attack envelope loop with a fadeout, or by using the fadeout option directly. Outside of these guidelines, allow yourself to go nuts. Also, although you may want to make a standard envelope and use it for every loop, feel free to make a unique envelope for each. Remember, there are no rules.
Step 6) Track something! The effect sounds best when you use enough channels so that the sustain on each loop has enough time to die off completely, especially if you track with sequential instruments. One loop will mix with the next while it's dying off, and you have a clean filter sweep.
That's it. Congratulations, you've performed reconstructive surgery. What have we gained by this method? Much. We've taken a plain old key-hit synth and turned it into something completely different; something totally original; something totally fresh and new. Not only that, but now you can move stepwise through the filter effect with direct correlation to the rhythm of your tune. The unification of filter and rhythm has been reestablished. w00w00!
theHacker [KFMF/Ultrabeat/FYooZHeN]
kgale@attila.stevens-tech.edu
10/24/95 @ 1:22am