On Kurzweil’s PC3 series synths, a layer of a sound program can have up to four “units” of DSP—measures of how hard the chips
work to create sound. You can spend DSP units on a modeled analog oscillator, a filter, or other synthesis building blocks. Thus, the PC3
is sort of like a virtual modular synth, only with DSP emulating modules, and algorithms (signal chains) acting like patch cords.
Things like the Triple Saw oscillator or four-pole filters use all four DSP units of a layer. Cascade Mode gets around this limit by running
one layer’s output into another layer’s DSP, with up to 32 layers in series. To illustrate this, we’ll run a Triple Saw oscillator into a series
of filters: four-pole lowpass, four-pole highpass, and finally, a sweeping allpass filter for a cool phasing effect. Dave Weiser
Click images for larger versions, after these online extras.
Step 1: Create the Triple Saw oscillator.
Start with program
SawMono,” a basic
template for virtual analog sounds. Hit Edit, go to the ALG page,
and select algorithm 5. Cursor down to the large single DSP
“block” and scroll the data wheel until you see “TRIPLE SAW.”
This oscillator generates three individual saw waves; one stays
in tune while the other two can be detuned for fatness on the
This might not make
sense initially, but go
to the DSPMOD page
and turn the level for this layer all the way down to –96dB. Now,
we’ll create a layer into which this oscillator can be cascaded.
Hit the left “more” soft button until you see a “DupLyr” soft button.
Hit this to duplicate the current layer, and you’ll find yourself
in Layer 2.
Step 2: Create and set the lowpass filter.
We’ve duplicated our
oscillator, but we need
this layer to be a filter.
Remain in Layer 2 and
go to the ALG page. Change algorithm 5 to 105. (Each PC3
algorithm has a Cascade Mode counterpart, referenced by the
original algorithm number plus 100.) Below that, select “Layer 1”
as the Alternate Input. Now you’re running Layer 1 into Layer 2.
(Toggle between layers with the +/- buttons to the left of the display.)
Move the cursor down to the DSP block and scroll until
you see “4POLE MOGUE LP.”
On Layer 2’s DSPMOD
page, set the
level at –15dB, filter
frequency (LP Frq) to
1,319Hz, and resonance (LP Res) to 7dB. With the cursor on
LP Frq, move to the source field at top right (Src1) and select
“Data” (slider A on the PC3) as the source—simply hold the
Enter button and wiggle the slider. Set the depth to 2,400 cents.
You’ll hear the Triple Saw oscillator through the filter, and be
able to sweep the filter with slider A.
Step 3: Create and set the highpass filter.
Duplicate Layer 2 the
same way you did
Layer 1, but first, turn
down its level on the
DSPMOD page. In Layer 3, go to the Alg page, select Layer 2
as the Alternate Input, and select “4POLE HIPASS W/SEP”
as the DSP block type
On the DSPMOD
page in Layer 3, set
frequency (HP Frq) to
98Hz and resonance
(HP Res) to 7dB. Keep slider A (Data) as Source 1 (it’s already
there since the layer is a duplicate), but raise its depth to 3,500
cents. When you move slider A, you’re now affecting the highpass
and lowpass filters. Raise the Level to –15dB in the bottom
Step 4: Create and set the allpass filter.
Duplicate Layer 3, but
this time, don’t turn
down its volume. The
way an allpass filter
works requires that it be mixed with a dry, unfiltered signal. In
Layer 4, select algorithm 108 with Layer 3 as the Alternate Input.
Make the DSP block “3POLE ALLPASS.”
Next, go to the DSPMOD
page. Make AP
Frq 988Hz, AP Width
0.400 oct, and AP
Sep1 (separation) 2,000 cents. Move the cursor in the left column
to the AP Frq row, then on the right, select LFO1 as Source
1 (hit keypad button 0 and scroll backwards—you’ll see LFO1
after a few clicks). Set LFO1’s depth to 2,000 cents. Raise the
level for Layers 3 and 4 to –6dB.
Step 5: Add some modulation.
On the LFO page in Layer 4, set rates of .30Hz minimum and 8.6Hz maximum. Set the
shape to “Sine.” To make a slider control the rate, wiggle that slider (I used slider B or
MIDI 13) while holding Enter. Varying the rate while playing adds a vibe reminiscent of
classic sci-fi or old Parliament albums.
You now have three detuned saw waves running into a series of three filters, with slider A sweeping the cutoff and slider B controlling the
rate of the phasing imparted by the allpass filter. Since we’ve used only four of 32 layers, your “virtual modular” setup can get a lot more
complex. Just repeat the basic workflow: Duplicate your layer, decide what “module” that layer will be on that layer’s ALG page, then tweak
the “knobs” of the module on the DSPMOD page. Happy programming!