Module 6 · Lesson 3 of 5

One knob, many shapes

Some filters have no fixed shape. Morph glides from low-pass through a notch to high-pass on one knob, the Multimode steps through fifteen modes, and the low-pass gate closes the tone and the level together, so it plays the note as well as filtering it.

16 minHeadphones or studio monitorsKiMiA and your keyboard

In this lesson you will

Sweep Morph from low-pass through the notch to high-pass
Step through the Multimode’s fifteen modes
Make a plucked, woody note with the low-pass gate

01Morph: three shapes on one knob

Choose Morph on the Type row and the Slope row turns into a Morph knob. It glides one filter through three of the classic shapes of Module 5: low-pass at 0, notch in the middle, high-pass at the top.

Figure 6.3.1

Morph: one knob from low-pass through the notch to high-pass

0 · Low-pass¼ · Low → Notch½ · Notch1 · High-pass

Cutoff 1 kHz · Resonance 40%, measured from the engine

Two different examples Audio example — listen in the online course

The Morph filter is the two-pole filter of the classic American four-voice synths of the 1970s, with their mode knob: low-pass at 0, the notch in the middle (the low-pass and the high-pass added at full level), high-pass at the top, gliding from one to the next at an even loudness. Because Morph is a Sound Matrix destination, a modulator or an envelope can sweep it while you play.

KiMiA’s Filter 1 panel with 06 · Morph Pad loaded and playing, its controls numbered — Filter 1 on Morph, caught at the notch: Morph reads Notch, and the curve dips at the cutoff. The bar under its slider is Modulator 1’s route, sweeping Morph back and forth, so while the pad plays the curve keeps changing shape.

Between the marks you get a blend, and the knob shows it (“Low → Notch”, then “Notch → High”). The notch is the low-pass and the high-pass added together at full level, so in the middle the bass and the treble both stay and only the band around the cutoff drops out. The loudness stays even all the way, so you can move Morph while you play without the sound jumping. The band-pass, which the original filter kept on a switch of its own, is KiMiA’s Band-pass type.

In KiMiA

Filter 1’s Morph knob is also a destination in the Sound Matrix (Filter 1 morph). 06 · Morph Pad routes Modulator 1, a slow triangle, to it: the pad walks from dark to hollow to thin and back over about seven seconds. Module 8 shows how to build that route yourself.

02Multimode: fifteen modes from one loop

The Multimode type follows the four-stage filter of the big multimode polysynths of the mid-1980s. It mixes the loop’s input and its four stages in different proportions, and each mix gives a different mode. Its Mode knob, in the Slope row’s place, has one every fourteenth of its travel, and shows each by name:

Figure 6.3.3

Four of the Multimode’s fifteen modes

Mode 0% · Low 4-poleMode 36% · Band 2-poleMode 50% · High 2-poleMode 64% · Notch

Cutoff 1 kHz · Resonance 30%, measured from the engine

The Multimode builds every mode from one four-stage loop, mixing its input and its four stages in different amounts, as the big multimode polysynths of the mid-1980s did. Its Mode knob has a mode every fourteenth of its travel: low-pass with 4, 3, 2 or 1 poles, band-pass with 4 or 2, high-pass with 1, 2 or 3, the notch, a phase shifter, and four of these with a gentle low-pass after them. Between two marks it glides from one mode to the next.

Mode on screen	Shape	Use it for
Low 4-pole to Low 1-pole	Low-pass, 24, 18, 12 and 6 dB	Round to open: pick the steepness by ear
Band 4-pole, Band 2-pole	Band-pass, narrow and wide	Narrow or wide nasal tones
High 1-pole to High 3-pole	High-pass, 6, 12 and 18 dB	Thinning a layer, gently or firmly
Notch	Notch	A hollow color
Phase	Phase shifter	Keeps every frequency, shifts them in time; moved, it sweeps like a phaser
High 2 + Low 1, High 3 + Low 1, Notch + Low 1, Phase + Low 1	The same shapes with a gentle 6 dB low-pass after them	A thinned or hollow layer with its fizz taken away

The Multimode gives the 6 dB and 18 dB slopes none of the other types have. Low 1-pole is the gentlest darkening in KiMiA, useful when a pad only needs its fizz taken away.

03The low-pass gate: a filter that plays the note

On most synths the filter sets the tone and the amplitude envelope sets the level. The low-pass gate does both at once. It comes from the West Coast synthesizers, which used a light-sensitive cell, a vactrol, to close a low-pass and a level together. KiMiA’s Low-pass gate (LPG on the Type row) models that cell:

Figure 6.3.4

The low-pass gate: tone and level close together

Low-pass, same envelopeLow-pass gate

Low-pass: the tone closes, the level stays

Low-pass gate: both close, slowly

Switch while it plays: same moment, different sound Audio example — listen in the online course

The low-pass gate is the West Coast synthesizers’ way to play a note: one light-sensitive cell (a vactrol) controls both the brightness and the level. Struck open by the filter envelope, it opens in about 3 ms and closes slowly, slower still as it nears the end, so the note dies away like a struck wooden bar. Half a second in, the gate is 32 dB quieter than a plain low-pass with the same envelope. The amplitude envelope can stay fully open: the gate makes the decay.

Three things set it apart from every other type:

Every note starts with the gate closed. The Cutoff, plus everything that moves it, decides how far it opens. From about 4.6 kHz up it plays at full level; below that, the lower the cutoff, the quieter the note.
It lags. It opens in about 3 ms and closes slowly, more slowly still as it nears the end. That lag is what makes the decay sound woody and natural.
Resonance stays gentle: it adds a little body, never a whistle.

So the way to play it is a low Cutoff and a big, short strike from the filter envelope. 06 · Gate Pluck sets the Cutoff to its lowest, the filter envelope to 95% with a short decay and no sustain, and leaves the amplitude envelope fully open. Each note is struck open and dies away like a marimba or a bongo.

Pro tip

Touch → brightness works wonders on the low-pass gate: harder playing opens it further, so it gets brighter and louder, as a struck instrument does. Try 2 octaves on 06 · Gate Pluck.

04Try it

Walk the shapes. Load 06 · Course Init. Set Type Morph, Cutoff 1 kHz, Resonance 40%. Hold a note and turn Morph slowly from Low-pass through Notch to High-pass. Listen to each shape as the knob names it.
Feel the moving pad. Load 06 · Morph Pad and hold a chord for half a minute. Then set Resonance to 70%: does the movement get clearer?
Pick a slope. Load 06 · Course Init, Type Multimode, Cutoff 1.5 kHz. Play a chord and step Mode from Low 4-pole to Low 1-pole. Which steepness suits a pad, and which a lead?
Play the gate. Load 06 · Gate Pluck and play a fast melody. Then raise the filter envelope’s Decay from 0.28 to 0.8 s, and finally raise Cutoff to 2 kHz: why does the pluck stop dying away?

Your notes · your favorite Multimode setting and what you would use it for

05Check yourself

Q1On the Morph filter, which shape do you get with the knob at the top?

Morph goes low-pass at 0, notch in the middle and high-pass at the top.

Q2You want a 6 dB low-pass, gentler than any 12 dB slope. Where do you find it?

The Multimode’s first four modes are low-passes with 4, 3, 2 and 1 poles, which is 24, 18, 12 and 6 dB an octave.

Q3You load the low-pass gate, set Cutoff to its lowest and the filter envelope amount to 0. What do you hear?

A low Cutoff keeps the gate almost closed, and on this type the level falls with the opening. Something has to strike it open: the filter envelope, your touch or a modulator.

Q4Why does a note through the low-pass gate die away so naturally?

As in a struck wooden bar, the highs fade before the body, and the last part of the decay lingers. The vactrol’s lag does exactly that.