Kurzweil:Tutorial- AllPassShape

From Sonikmatter

This is more of a transcript of events than a tutorial, during a chat session between myself and TogaKure99.

I forget what Toga was talking about, but eventually he said "ah, now I wanna mess with my kurz". So i said, hey, pass me all the params you come up with, so I can learn. A few moments later, he says "wow, you can really hear the overtones when you run an AllPass thru a Shaper." He fills me in on the alg, and parameters he's using:

1. Algorithm 5
2. Keymap 151 Sawtooth
3. 2 Pole Allpass BLOCK
4. Shape 2 BLOCK

He then tells me to set the FRQ to D5, the WID to 0.2ct, and the AMT to 0.3x. For me, that sounds like a pretty buzzy sawtooth. I'm not sure what I'm hearing at this point, so he explains that the shaper is adding a bit of distortion to the signal, while enhancing the presense of the upper partials of the sawtooth. he says "put a slow LFO on the frequency, and listen to that"

So, I set the FRQ src1 to LFO1, and the depth to 1200ct. Going to the LFO page, I set the LFO1 to 1.00hz, using the Sine shape.

Sounds like one of those old-school filter-swept brash moog bass synth sounds, a bit. You can really hear the upper partials being accentuated. I mess around with slowing the LFO down even more, and speeding it up, too. Setting the LFO to something like 0.2hz really lets you hear the sweep.

Now, I start playing this sound really low on the keyboard, like in the lowest octave and it is nice. But i don't really like the sound of the LFO controlling the sweep. I only like the first part of it, when it rises at the beginning of the cycle, to the highest point. I ask him about this, and he says he's too tired to do the math to figure it out. So, I do it myself :-P. Because I don't want to lose my settings for the LFO, I stick it on SRC2 [LFO1, 0ct, 1200ct], with a DptCtl of OFF. that way it's still there, just not being used to modulate the sound.

A sine wave is a circle that's been stretched out onto a 2D plane. So, since I only like the first part of that circle which is the first 90 degrees of the cycle, I think about what that 1/4 of a circle looks like, and start building an ENV2 that looks like that. Since the LFO is at 1.00hz, and I only like the first 1/4 of that, my ENV2 is only gonna be 0.25s long. Here are the values I came up with for this mock 1/4 circle:
[0.08, 65%] [0.12, 100%] [0, 0%] [0.02, 56%]
That's for ATT1, 2, 3 and Decay. Everything else is zero'd out.

now that sounds pretty awesome. I've got my 1/4 circle filter sweep, without having to deal with the LFO Sine cycle controlling it. But it doesn't sound like a punchy, staccato bass, because the sound itself doesn't have a fixed duration.

So I ask Toga about that, and the decision is to use the AMPENV to fix this. So, jumping into the AMPENV, I decide on these values, after some experimentation with figuring out how to get it to decay to 0% after a short period of time:
[0, 100%] [0.18, 100%] [0, 0%] [0.12, 0%] (Att1, 2, 3, Dec)
So, basically, the sound runs at 100% volume for 0.18s then drops to 0% over a period of 0.12s. total time is 0.3s for this. That's pretty short and punchy. But it's a little too short and punchy. So, instead of finding new values for everything, it's more interesting to make a slider control the envelope time. Jump to the ENVCTL page, and set SliderB to Source for Att:, and play around with Depth for a bit. Setting the depth above 1.00x will make the attack time run faster than 0.18s (0.18 / 1.x). So, I play around a bit, and end up setting it to 0.270x. So, now my Attack time can be super short (0.18s) or a little longer (0.66s).

By this point, we've only been messing with this sound for about 5-10 minutes. This doesn't take any time to figure out. I'm pretty happy with the bass sound, but it doesn't sound fat enough for me. So, it's back to the FRQ page for more tweaking.

First things first, get rid of the ENV2 cycle, so I can not hear any modulation on the base sound. Step2, tinker with the FRQ values until I find the sweet spot for fat bass goodness. It is discovered between A5 and E5. Being the nerd that I am, I figure out that the difference between the two points is ( 659hz - 440hz). So, I set SRC1 to SliderA, and Depth to the closest values for that amount, which ends up being 250ct. Now, SliderA controls the FRQ exactly between A5 and E5, the money zone for this sound.

Everything sounds good on the FRQ page, but I'm not sure what WID and AMT do, so I go play around with those Adjust values. The higher I push the AMT, the more distortion comes into the sound, and less pitch. WID doesn't really seem to make that much difference, just affecting how fat or narrow the sound is. I settle on using 0.010ct for WID, and 0.675x for AMT.

Well, there it is. A decent bass sound. It sounds really harsh and brittle way up high (above C4), so I set the Range to C0-C3. Discoveries occur, though, when I start playing octaves. this is a HUGE bass sound when it's octavized like that. So, I duplicate the layer, and change the PITCH:Adjust on layer 2 to +12ST. now we have awesome awesome fatty bass goodness.

Toga is still messing around with his version, but he says "this thing sounds uber Fat thru a flanger". I'm fairly new to KDFX, but I know how to build a studio from scratch, even though I don't know what most of the params do. So, I hit up Studio 199, edit it, and add ALG 154 Flanger 1 to FXBus1, and start vamping. This thing is HUGE. that's the sound right there. total 70's Stevie Wonder "SuperStition" bass meets disco meets 90's trance.

So, there it is. Here is a recap of the params I ended up using for the sound, not every param that I went thru:
Keymap: 151 Sawtooth
Keyrange: C0-C3
Alg5: 2Pole Allpass -> Shape2
FRQ: E5, Data -250ct
WID: 0.010ct
AMT: 0.675x

AMPENV: Att2 [0.18, 100%] Dec [0.12, 0%]
ENVCTL: Att: src:MIDI22 depth:0.270x

Duplicate the above, and put PITCH:Adjust to +12ST for layer 2.

KDFX: put Alg 154 Flanger1 on FX1 in studio 199

The output for this program is pretty hot, so set the output for each layer to 12db, or less. A fat bass sound that uses 2Pole All Pass, and Shape2 for it.

peace.

chuck

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