Holy Bot

Bedroom music production, gaming and random shit


volca keys

I made this with an old friend. Angry German kid, hard synths and tripping drums. Deutsch Schwedische Freundschaft.

I made this with an old friend. Angry German kid, hard synths and tripping drums.

Smod (with Katrin Hesse)

In lack of a real article here’s the corner of the bedroom. Not much have actually changed sinced the last man cave shoot. (I’ve bought and sold some gear, such as another SH-101, another Juno-106 and a Kick Lancet.) The latest addition to the setup is the mighty Analog Four. I’ve also made a couple of tracks in this corner of the world. The item on the far left of the desk is a sewing machine – not mine though.

Small Sawtooths and Low-Pass Filters

I got a few small analog synths that I put next to each other for comparison. The test pattern is defined as follows:

  1. The raw sawtooth waveform of the synth, 100% open frequency cutoff and resonance at null.
  2. Manual filter cutoff sweep, resonance at 0%.
  3. Manual filter cutoff sweep, resonance at 50%.
  4. Manual filter cutoff sweep, resonance at 100%.

The input levels are adjusted to roughly peak at -6 dB on each audio clip (maybe that was a bad decision). All synths were connected to a Mackie 1202VLZ4 mixer before being recorded using high-grade Cirrus Logic converters. No normalizing was added in post.

First is the Korg volca keys. When resonance is added, the volume is intensely boosted. The filter section uses the circuitry of the Korg miniKORG700S (which used dual 12 dB per octave low-pass and high-pass filters that were combined). Given the 128 steps that can be controlled via MIDI, the filter sounds very steppy on high resonance (peak).

Next is the Korg volca bass with the second and third VCOs muted. I’d say it has a little buzzier tone than the volca keys. Its filter is also much smoother, especially on high resonance. It’s a fine-tuned analog filter with a bright and crisp sound, with the resonance going from a clean peak to an increasingly distorted sound. As for the volca keys, the volume jumps with resonance.

The toyish Gakken SX-150 Mark II has a quite nice thick tone, with low resonance that is. Slightly less bottom end content than the volca modules perhaps. Unfortunately the pitch slides some due to me messing up operating the stylus pen. Raising the resonance seems to lower the overall volume. With filter cutoff set to fully open and resonance at 100%, the filter is making a loud noise (hiss). I think the synth has a voltage-controlled filter, Sallen-Key low-pass type, 12 dB per octave.

As a bonus the Yamaha CS01 from 1982 is included. The oscillator (labeled VCO, but is in fact a digital tone generator) lacks of woof and weight compared to the others. The first audio clip is the sawtooth 100% open frequency cutoff and resonance set to low (this model is equipped only with two resonance settings). The high setting follows after. The filter is a 12 dB resonant voltage-controlled filter.

Not sure what conclusion could be drawn from this, if any. However, there are some discussions about which of the volca modules are the best sounding et cetera, and maybe this could help deciding. Although this is just a comparison of their isolated sound engines and filters. Interface, voicing options and such have not been regarded.

P.S. You might be interested in a low-pass filter test I made, running a SH-101 trough the filters of a MiniBrute, a Minitaur and an Analog Four,

Analog Sound Designed

Here’s a breakdown of a song that you maybe can learn something from. It’s not that profound, but should give you some hints of the sound design.

But first, listen to, so you can follow the article.

The song itself is fairly minimal and only consists of a few channel tracks, and therefore easy to analyze.


For the drums I used an old Roland TR-606 drum machine sequenced to the tempo of 110 BPM. I also added Boss DR-110’s hand clap and a slightly downpitched snare drum for the drum roll.

I put rhythm first in most of my songs, even if this particular pattern isn’t that complex.


The pounding bass is created on the Korg volca bass.

There are two VCOs grouped, an octave apart, playing the main ostinato, and the third VCO is introduced later in the song as a live pitch. In this case the effect of the VCOs sharing a common envelope and stuff renders a nice effect, where the gate length sounds chopped while the rhythm is intact.

The filter cutoff is slowly modulated by the LFO to make some movement in the sound.

During the crescendo, the filter is manually opened up to two-thirds – and what a liquid filter it is.

A quite high resonance is applied to make the bass scream a bit.

The bass channel is side-chained (triggered by the kick drum) and duplicated to a parallel channel, with bass rolled off (using a high pass filter) and fed through a phaser effect to enhance the stereo image and add further movement.


The motif is a minimal, almost atonal, figure made on the Korg volca keys. The synth is best used for plucky shit, and set to poly ring voicing (square waves through a ring modulator). The noisy internal delay is bypassed, in favor of an external digital reverb with a plate algorithm.


This is sequenced internally on the Roland SH-101. Mixed waveforms are used and noise modulation of the VCF for that gritty sound. Cutoff sweeps are manually made and pretty randomly so. Also with high resonance level to add an acid touch. There’s not much use of the sub oscillator here, because the arpeggiator shouldn’t collide with the bassline.


Only two notes where played twice on the Yamaha CS01, and they are almost unmotivated. Nevertheless, they sound good – yeah, it’s that notorious PWM sound.


This is the small but big Moog Music Minitaur producing a 8-bit colored sound. The synth is run by a software monophonic arpeggiator which makes these octave jumps when programmed with more notes that it can handle.

I’m ready now.

Japanese Synthesizer

So I got this package in the mail today. Really just a toy. Maybe not so musical but still a true analog synthesis that’s up to no-good-lush-creamy-noise. Who doesn’t need that? It also features a stylus controller and built-in speaker. And check out the price tag. It fit quite nice next to the volca range (but sounds very different and is more chaotic). Yes it’s the Gakken SX-150 Mark II.

Faux Step Recording

The volca keys lacks a real step recording such as the bass module, but it’s still possible to program keys in a similar fashion. Activate one step and record note(s) and pot movements, then turn it off and do the same thing on the next step. Here’s the workaround:

  1. Clear sequence, press FUNC + CLEAR ALL.
  2. Enter active step mode, press FUNC + ACTIVE STEP.
  3. Turn off all steps but the first.
  4. Turn on motion sequencing, press FUNC + ON/OFF
  5. Turn off flux if necessary, press FUNC + FLUX.
  6. Leave active step mode, press FUNC.
  7. Press PLAY + REC and choose note(s) for this step. You can also set the filter et cetera if you like. You might have to hit REC a couple of times to get it right.
  8. Turn off recording, press REC, and enter active step mode again, FUNC + ACTIVE STEP.
  9. Turn on the next step and turn off the step you just edited.
  10. Repeat step 6-9 for as many steps as you like the sequence to loop.
  11. When all steps are edited, turn them on, press FUNC + ACTIVE STEP + all steps.
  12. Exit active step mode, press FUNC, and then press PLAY.

Bass for Dummies

Here’s  a song I’ve made with the volca bass and keys,

The bass sound is actually programmed in Step Mode as a simple pattern in 1/16 notes, and then resampled a few times with different manually movements. There are not many effects on the bass, just a multiband compressor and a little Haas for stereo width. (Then of course side-chain, triggered by the kickdrum.)


The bass sound is made on the volca bass. First group all three VCOs together (VCO GROUP) and turn them on (VCO1, VCO2 and VCO3 lit). Leave PITCH 2 off but detune PITCH 1 (down) and PITCH 3 (up) for a thick unison effect. Have the first (VCO1) and second (VCO2) oscillators generate a sawtooth wave and the third a square wave (VCO WAVE).

On the low-pass filter section (VCF) you’ll need a little resonance to make the LFO go well into audio range, so put PEAK level on 11 o’clock.

Set CUTOFF frequency at 11 o’clock. (As for knob movement, slightly raise CUTOFF level at the same time as EG DECAY/RELEASE drops.)

Now, set the LFO RATE to max and TARGET to CUTOFF modulation. Adjust intensity (INT) to 9 o’clock or so. This little trick – modulating the filter cutoff point (or pitch) with an audio range oscillator – introduces some buzz or grit (read: distortion) to the sound. And if you turn down the intensity a bit, you will get a fat analog sound.

Turn on the envelope generator for volume (AMP EG ON). On the EG section, set ATTACK to null, DECAY/RELEASE to 1 o’clock – turn this knob to about 10 o’clock and back again – and CUTOFF EG INT to 10 o’clock.


There were two technical problems with recording the volca modules: first MIDI latency and second, mono recording.

I’ve spent an hour or two trying to solve the MIDI offset, but didn’t succeed. In the end I just ignored it. (Well, someday I will fix it, for sure.)

And about the mono recording. The volca modules (bass and keys) are each a 3 VCO strong monosynth, and both of them have a stereo audio output. I can’t make much sense of this, but I could connect the each device to (A) a mono or (B) a stereo pair input on the audio interface (Propellerhead Balance). I chose to mono to save input ports. Moreover, I’ve read somewhere that the so called stereo, is just one mono signal rendered as left and right. This might be wrong though.

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