Adventures in Synthesis: Generative Modular Synthesis (Pure Data + DIY Hardware Modular)

Published on Jul 5, 2017 Chris Beckstrom

"TL;DR?
This is a patch that plays itself. I make a few adjustments but for the most part this is bleepy bloopy self-playing modular synthesizer music.

Download my PD modular here (free and open source!):
https://github.com/chrisbeckstrom/pd_...

Download this specific patch:
https://github.com/chrisbeckstrom/pd_...

I've been building a modular synth inside the free and open source software Pure Data, and lately I've been experimenting with ways to integrate my physical modular with it. Using a combination of audio, MIDI, arduino, linux tricks, and some other stuff, I got them humming together nicely.

The PD gui lags wildly with everything going on - I'll have to figure out how to prevent that sort of issue. But it sure is fun to hear it in action!

This patch is so complicated I couldn't accurately describe each part of it. Basically there is a master clock (a software VCO) which is routed all over the place, including into my real life modular via an arduino. All the other rhythms divided from that pulse using dividers, random gates, probability modules, etc. Also I plugged a radio into the modular, which gets in the mix and ends up back in Pure Data before everything is mixed and recorded right to the video."

Adventures in Synthesis: Glitchy Shift Register Feedback

Published on Dec 19, 2016 Chris Beckstrom

"I'm finishing up a techno album at the moment (which we be available for free at chrisbeckstrom.bandcamp.com soon!), and thought it would be refreshing to make some nonrhythmic music with my modular. This is a patch that some might not even consider music- and that's ok. We can agree to disagree.

These glitchy, distorted blips and beeps are a pretty good aural expression of how I feel about 2016.

PATCH NOTES
This patch is based on a bunch of feedback: things modulating other things modulating other things which eventually find their way back and modulate the first thing. When I try to do this on the computer I end up crashing everything. With analog circuits there is nothing to crash: it sounds awesome.

The pitch of an oscillator is modulated by the output of an R/2R resistor ladder, which is receiving gate signals from a 4-step shift register. The shift register is clocked by a square oscillator. The input of the shift register- the thing that gets it going, so to speak- is the output of a clock divider which is listening to the triangle wave coming out of the original oscillator. (It's not really a triangle wave- it's more of a rounded square wave, so the clock divider has no trouble spitting out divisions.) In this way there is a feedback loop: the oscillator speed is controlling its own rate of modulation! This accounts for the periods of silence or relative stasis. A few times throughout the video I make the oscillator go faster, which in turn modulates itself more, causing more activity. Turning the big oscillator knob to the left slows everything down.

Two wave outputs of the main oscillator- square and triangle- are routed into three inputs of a sequential switch. The third input to this sequential switch is the output of a saw wave oscillator. This saw wave oscillator's pitch is modulated by a 10 step sequencer, which in turn is clocked by the pulse output of the main oscillator. The sequential switch is clocked by another divided output of the main oscillator, again causing a feedback loop. The fourth input to the switch is the output of a module I call "space noise," which is really just a bunch of square wave oscillators making clicking sounds. I often use it for random modulation at slower rates; at faster rates, it's just noisy clicking.

As the sequential switch steps through each of its four channels, we're basically hearing each input in order: first the "space noise" clicking, then the main square wave oscillator, then the saw wave, then finally the triangle from the main oscillator. When the sequential switch is clocked slowly, we can hear each wave as if we were muting and unmuting four channels on a mixer in order. At fast speeds (audio rates) we hear the four outputs as a single wave. This phenomenon- things sounding completely different depending how quickly we hear them- never ceases to amaze and entertain me.

Finally, the saw oscillator (step three in the sequential switch) is being modulated by another 10 step sequencer, which is in turn clocked with yet another square wave oscillator. The clock divider which is clocking the sequential switch is receiving reset messages (gates) from the "space noise" module, which causes the clock division to become a bit random and glitchy.

The mono output of the modular goes into a mixer and some of the modular is sent to a vintage (90's!) Alesis Microverb II digital reverb, which is brought back into the mixer on two channels for some nice stereo. I like the combination of gritty analog sounds and gritty digital reverb. The Microverb came from a church, and I can guarantee they never put anything like these sounds through it."

Adventures in Synthesis: Backyard Fall Afternoon Modular

Published on Sep 27, 2016 Chris Beckstrom

"I'm on a mission to challenge some ideas about modular synthesis:

That is has to be expensive, or that you can't build it yourself, or that it has to look pretty, that it's too complicated, that you need an electrical engineering degree to play it, or that you can't take it outside.

After all, it's a musical instrument not totally unlike a guitar. Now that I've reconfigured it a bit, why not bring it out to the back yard and play a bit?

This simple patch was inspired by the work of Kaitlyn Aurelia Smith. If you haven't heard her magnificent music, check it out!

Patch Notes

There are 4 voices in this patch: The bassline, a 3-note repeated figure by saw waves, the delay of that figure, and another saw oscillator.

CLICK FOR MORE »

Demo: Square Wave Oscillator Prototype

Published on Mar 5, 2016 Chris Beckstrom

"I'm considering building and selling sound-making electronic gadgets. Here is a prototype of an analog square wave oscillator that can be used as a regular oscillator or a clock.

This prototype gets power via 12V wall wart, and the power connections are brought to the panel via bolts so the device can be used as a bench power supply.

It's handmade, lofi, and in keeping with the DIY aesthetic, constructed out of reclaimed materials and decorated with sharpies."

CB's DIY Modular Synth: 2-16-2016 Arduino oscillator, MIDI, and PT2399 digital delay circuit

Published on Feb 16, 2016 Chris Beckstrom

"More about this project:
http://www.chrisbeckstrom.com/portfol...

This week I built two very exciting modules: an Arduino-based digital oscillator with MIDI input (!!!) and a PT2399-based digital delay circuit. Still working out some kinks on the Arduino oscillator, but for now it has 3 programs, each with a crossfade between different waves. Program, frequency, and wave shape (crossfade) are all voltage-controllable. In addition, the Arduino spits out gate voltages when it receives MIDI note on messages, which I can then use to trigger envelopes, sequencers, etc.

This particular patch is a MIDI sequencer generated by Qmidiarp on linux whose root is determined by the little MIDI over USB keyboard, then sent via MIDI cable to my Arduino oscillator. The output of that goes into an amp (the Arduino is pretty quiet) and then into a VCA whose attenuation is being modulated by the gate voltages. Then into a mixer along with some delay. A triangle LFO is also modulating the frequency of the oscillator (when it's in "free" mode) and a slope generator triggered by the gate voltages is modulating the wave shape (sine to saw, tri to saw, and sine to wave-folded sine)"

FYI, I created a new Chris Beckstrom label for these moving forward. You'll find three previous posts there. A search on Chris Beckstrom will bring them up as well, along with two Bitwig videos. Lots of "New" labels for this post.

"Engine 40106" – Live modular techno (CB's DIY Modular Synthesizer)

Published on Sep 3, 2015 Chris Beckstrom

"High quality audio available here:
https://chrisbeckstrom.bandcamp.com/t...

I recently built a drum module and repaired a noise module, which inspired me to make some analog techno. I started this project on a whim and never thought I'd get this far! It's time to make some music with the collection of modules I've built.

Performed live (no edits) on my homemade modular synthesizer.

Recorded through an old analog mixer (with a splash of spring reverb) into Ableton Live.

More about this project here:
https://hackaday.io/project/5826-diy-...

and here:
http://cb.hopto.org/cbfishes/2015/05/...

The bass drum circuit and CMOS noise generator circuit (the two main sounds in this track) are more or less straight out of Elliot Williams' Logic Noise series on Hackaday.com. Check it out here:
http://hackaday.com/tag/logic-noise/"

CMOS Noise Percussion (CB's DIY Modular Synthesizer)

Published on May 15, 2015 Chris Beckstrom

"Early this morning I built a new module: a CMOS-based metallic noise generator. Inspired by this awesome Hackaday post by Elliot Williams:
http://hackaday.com/2015/04/10/logic-...

A series of 6 40106 square wave oscillators get mashed up with each other through a 4070 quad XOR, and what comes out sounds metallic and noisy and great! I don't really understand what the XOR is doing, but it sounds a lot like ring modulation.

From what I gather this is similar to the analog cymbals on the famous TR-808 drum machine. It even uses the same chip for the oscillators! Who knew you could build it yourself for about $2?

I tweaked the circuit a bit: Instead of a pot for each oscillator, 3 pots control 3 oscillators, 3 oscillators have a fixed frequency, and I added an external input to add additional cacophony (with a switch to go back to 3 oscillators). Soon after installing the module in my synth I realized a running a melodic sequence into that input makes it sound like pitched metallic drums. Cool! Depending on 3 knobs that control the oscillators it can sound like a single tone, cowbell, toms, noise, cymbals, and even dialup-style sounds.

Here is a quick iPhone (and iPhone mic) video of the module in action. I'm running the noise through a low pass gate that is controlled by audio clicks coming out of my computer– a super lo-fi synchronization, but it works. The bass drum and snare are TR-808 samples playing in Ableton Live, everything else is my new CMOS Noise module. This could go great with a bass drum and snare drum module.. Guess I better get back to soldering.

Thanks Elliot Williams @ Hackaday!! What a great circuit."

The Many Sounds of Analog Synthesis (CB's DIY Modular Synthesizer)

Published on May 5, 2015 Chris Beckstrom

"A collection of patches that demonstrate the variety of sounds my synthesizer can make. All sounds are made by the synth except for a splash of spring reverb.

For more about this project:
http://cb.hopto.org/cbfishes/2015/05/...

Here is each patch from the video:
0:00 Shotgun-shell Light "Theremin"
0:41 Acid bass sequence
1:20 Tuned Noise
1:42 Weird Resistor Ladder Sequencing
2:09 Big Thick Drone
2:31 Playing my Stylophone-style Keyboard
2:51 Playing the keyboard with fingers instead
3:08 Cowbell!
3:29 Laser bass drums
3:45 10 step sequencer as oscillator
4:10 Manual and clocked arpeggios"

Chris Beckstrom's DIY Modular Synth- Improvisation 5/4/2015

Published on May 4, 2015

"Improvising with my DIY modular analog synthesizer. I've been building this synth for a few months now, now it's time to learn to play it! Here's some improvisation/noodling from this morning. The synth was recorded live through an analog mixer (with a touch of spring reverb) into Ableton Live."

Interesting bit via CB's website:

"My approach to building the modules– the various musical Lego bricks– was to use the simplest circuits possible and keep the per-module features low. I wanted each piece to do one thing well; before starting this project I had zero electronics experience, zero understanding of the inner workings of synthesizer hardware, and zero math skills. I reasoned that if I created one thing at a time, eventually I would have enough modules to make some sounds. Keeping the features low helped me keep the circuits simple. If any experienced DIYer looked at my circuits they’d see how laughably simple they are, but in the end it doesn’t matter. All that matters is the sounds that come out!

So far I’ve probably put about $100 into this instrument, most of that expense coming from the electronic components themselves. Aside from the Monotron I panel-mounted, everything was built from raw components following schematics I found on the internet. No kits. I’ve altered most of the circuits to cooperate with the rest of my synth– removed capacitors here, added resistors there– completely by trial and error. I don’t have an oscilloscope, so the main way I test things is by actually using the synth (to hear if the LFOs are working correctly, I have them modulate an oscillator). I think this is a different approach than some electronics enthusiasts who rely mostly on the oscilloscope to show them what is happening. So far it’s mostly worked– aside from the hours spent troubleshooting circuits that didn’t work..."