Module 5 · Lesson 3 of 5

Two filters

Every KiMiA layer has a second filter. Put the two in a row and you set the bottom and the top of a band; put them side by side and you get two peaks; let one envelope move them in opposite directions and a note changes shape as it plays.

15 minHeadphones or studio monitorsKiMiA and your keyboard

In this lesson you will

Switch Filter 2 on and choose how it works with Filter 1
Set the bottom and the top of a band with two filters in series
Make two peaks with two filters in parallel, and move the filters in opposite directions

01Filter 2

Each layer has a second filter on the Edit›Filter 2 · routing panel, beside Filter 1. It has the same 19 types, its own Cutoff and Resonance, and one more row that Filter 1 doesn’t have: Routing, which decides how the two filters work together.

Figure 5.3.1

KiMiA · Edit · Filter 2 · routing

① Type, the same 19 as Filter 1 · ② Slope · ③ Cutoff and Resonance · ④ Envelope amount (Filter 1’s envelope, by Filter 2’s own amount) and Key tracking · ⑤ Routing · ⑥ Parallel balance, in use when Routing is Parallel. The switch in the panel’s title turns Filter 2 on and off.

The sound path of 05 · Crossing Filters: Source Saw · Pulse, Filter LP 500 · F2, Amp and a plate reverb, with the filter envelope moving Filter 1 and Filter 2 cutoff — The sound path of 05 · Crossing Filters. The Filter stage reads LP 500 · F2: Filter 1, a low-pass at 500 Hz, with Filter 2 switched on too; and the box above it shows the filter envelope moving both cutoffs.

KiMiA’s Filter 2 · routing panel with 05 · Crossing Filters loaded, each control numbered — Filter 2 has its own settings for everything but Drive and Touch → brightness, which belong to Filter 1. Routing decides how the two meet.

Filter 2 starts switched off. Turn it on with the switch in the panel’s title; off, it costs nothing and keeps its settings, so you can compare a sound with and without it at a click. Its Envelope amount follows the same envelope as Filter 1 (Lesson 5.4), by its own amount, and its Key tracking works as Filter 1’s does.

02In series: a band with a bottom and a top

With Routing at 1 → 2 the sound goes through Filter 1, then through Filter 2 (2 → 1 the other way round). Each filter takes its share, so a low-pass followed by a high-pass leaves only what lies between their cutoffs: a band whose top and bottom you set separately.

Figure 5.3.4

Two filters in series: a band with its own bottom and top

Filter 1 · Low-pass 24 dB · 3 kHzFilter 2 · High-pass · 400 HzBoth · Routing 1 → 2

Filter curves, measured from the engine

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

Each curve is KiMiA’s own: noise rendered through the filters and measured. In series the two curves simply add up: the band passes 1 kHz at −3 dB and turns 100 Hz down 24 dB and 10 kHz down 48 dB. The order, 1 → 2 or 2 → 1, made no measurable difference here (under 0.1 dB).

That is the sound of a small speaker: a telephone, a transistor radio, a megaphone. It is also how a pad or a string layer stays out of the way. A high-pass at 200–400 Hz keeps it out of the bass, and a low-pass keeps it from fizzing above the vocals. Neither filter alone can do both.

In KiMiA

With the four classic types the order changes nothing: in our measurement, 1 → 2 and 2 → 1 gave the same curve. The order matters when one of the filters colors the sound as it is pushed, as the Ladder and its cousins do (Module 6): the second filter then shapes what the first one added.

03In parallel: two peaks

With Routing at Parallel the sound goes through both filters at once, and Parallel balance mixes the two results: Filter 1 alone at 0%, Filter 2 alone at 100%, half and half at 50%. Two band-passes in parallel give the curve two peaks, something no single filter of the four classic types can do.

Figure 5.3.5

Two band-passes in parallel: two peaks

Band-pass · 750 Hz · Res 70%Band-pass · 1.2 kHz · Res 70%Parallel · balance 45%

Filter curves, measured from the engine

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

In parallel the sound goes through both filters at once and the two results are mixed. Here the curve keeps two peaks, at 732 Hz and 1.2 kHz, with a dip of 5 dB between them: the first two formants of a sung “ah”, which the ear hears as a vowel. Parallel balance sets the mix, from Filter 1 alone at 0% to Filter 2 alone at 100%.

Two peaks are what make a voice recognizable. Your mouth boosts two or three regions of your vocal cords’ buzz, and where they sit decides the vowel. Move one band-pass and the vowel changes. The Vowel type (Module 6) goes further, with five peaks placed as a singer’s.

04Two filters, one envelope

Filter 2’s Envelope amount can be negative. Give the two filters opposite signs and the filter envelope opens one while it closes the other. In series, a low-pass opening and a high-pass dropping at the same moment let the whole sound through at the strike, then narrow it to a band as the note goes on:

Figure 5.3.6

One envelope, two filters moving in opposite directions

Low-pass 500 Hz · Envelope amount +55% → High-pass 1.6 kHz · Envelope amount −60% · in series

Audio example — listen in the online course

The two dashed lines are the cutoffs as the engine reported them. At the strike the filter envelope raises the low-pass to 2.3 kHz and pulls the high-pass down to 303 Hz: the whole sound comes through. As the envelope falls, both go back to where they were set, and the note narrows to the band between 500 Hz and 1.6 kHz.

Pro tip

Use this for any sound that should start full and end focused: a plucked lead that thins out as it rings, a brass stab that blooms and then sits back in the mix, a bell whose body fades before its shimmer. The envelope’s Decay (Lesson 5.4) sets how fast the band closes in.

Recipe	Filter 1	Filter 2 · routing	Result
Telephone voice	Low-pass 3 kHz, 24 dB	High-pass 400 Hz · 1 → 2	A narrow, boxy band like a small speaker
Clean layer pad	Low-pass 4 kHz	High-pass 250 Hz · 1 → 2	A bright pad that stays out of the piano’s bass
Two-peak “ah”	Band-pass 750 Hz, Res 70%	Band-pass 1.2 kHz, Res 70% · Parallel, balance 45%	Two peaks, close to a sung “ah”
Full, then focused	Low-pass 500 Hz, Envelope +55%	High-pass 1.6 kHz, Envelope −60% · 1 → 2	Full at the strike, then a narrow band

05Try it

Build the telephone. Load 05 · Course Init. On Filter 1 set Low-pass, 24 dB, Cutoff 3 kHz. Switch Filter 2 on: High-pass, Cutoff 400 Hz, Routing 1 → 2. Play a melody in the middle of the keyboard, then switch Filter 2 off and on again.
Move the band. Load 05 · Telephone Lead. Raise Filter 2’s Cutoff toward 1 kHz, then lower Filter 1’s toward 1.5 kHz. How narrow can the band get before the sound stops being useful?
Make it talk. Load 05 · Two Peaks and hold a note. Move Filter 2’s Cutoff slowly between 800 Hz and 2 kHz: listen for the vowel changing. Then move Parallel balance from 0% to 100%.
Cross the filters. Load 05 · Crossing Filters and play short notes. Set Filter 2’s Envelope amount to 0, then to −60% again: what does the high-pass add to each strike?

Your notes · the narrowest band you still liked

06Check yourself

Q1Filter 1 is a low-pass at 3 kHz, Filter 2 a high-pass at 400 Hz, Routing 1 → 2. What do you hear?

In series each filter takes its share: the low-pass removes what is above 3 kHz, the high-pass what is below 400 Hz. What is left is the band between them.

Q2When does Parallel balance do anything?

In series the sound passes through both filters one after the other, so there is nothing to mix. In Parallel, the balance mixes the two filters’ separate results.

Q3Which routing gives a curve with two separate peaks?

Each band-pass makes one peak. Side by side, their results are mixed and both peaks remain. In series, each would cut away the other’s peak.

Q4Filter 1’s Envelope amount is +55% and Filter 2’s is −60%. What happens at the strike of a note?

Both filters follow the same filter envelope, each by its own amount. Opposite signs move them in opposite directions.