Adding MIDI To A Mini Synth Is Easy As Pi

There are a handful of relatively dirt cheap synths out there like the KORG Monotron, but many of them use ribbon controllers that aren’t very precise.  Ribbon controllers basically slide pots that you operate with your finger or a stylus.  They’re painted to look like piano keys in order to show you approximately where the notes are supposed to be. The Stylophone is another extremely affordable synth that does even less as a synthesizer and uses this type of input. It’s a fun input if you don’t mind imprecision, but can be annoying otherwise.

[schollz] isn’t satisfied to synth this way, so they added MIDI input to their KORG Monotron using a Raspberry Pi and a DAC. Fortunately, the Monotron is quite the hackable little synth, with nice, big, labelled pads on the PCB.

All it really took was a couple of solder joints in the right places, plus a clever Python script. The script listens for MIDI input from a keyboard, and then controls an MCP4725 DAC, which sends voltages to the Monotron. [schollz] wrote a tuning function that computes the FFT of the MIDI tones to find the fundamental frequencies of each to send along to the Monotron. Check it out after the break.

If liquid control is what you’re after but all you have is a keyboard, try making your own ribbon controller.

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Hacked Prosthesis Leads To Mind-Controlled Electronic Music

As amazing as prosthetic limbs have become, and as life-changing as they can be for the wearer, they’re still far from perfect. Prosthetic hands, for instance, often lack the precise control needed for fine tasks. That’s a problem for [Bertolt Meyer], an electronic musician with a passion for synthesizers with tiny knobs, a problem he solved by hacking his prosthetic arm to control synthesizers with his mind. (Video, embedded below.)

If that sounds overwrought, it’s not; [Bertolt]’s lower arm prosthesis is electromyographically (EMG) controlled through electrodes placed on the skin of his residual limb. In normal use, he can control the servos inside the hand simply by thinking about moving muscles. After experimenting a bit with an old hand, he discovered that the amplifiers in the prosthesis could produce a proportional control signal based on his inputs, and with a little help from synthesizer manufacturer KOMA Electronik, he came up with a circuit that can replace his hand and generate multiple control voltage channels. Plugged into any of the CV jacks on his Eurorack modular synths, he now has direct mind control of his music.

We have to say this is a pretty slick hack, and hats off to [Bertolt] for being willing to do the experiments and for enlisting the right expertise to get the job done. Interested in the potential for EMG control? Of course there’s a dev board for that, and [Bil Herd]’s EMG signal processing primer should prove helpful as well.

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MIDI has been a remarkably popular interface since its inception way back in 1983. Based on existing serial interfaces, and with a broad enough set of features, it remains the defacto standard for communication between musical gear. However, older gear and many modular synths simply don’t grok digital data, instead using analog control voltages to get the job done. Never fear, though – you can convert from one to the other with the goMIDI2CV.

It’s a simple device, hewn from an ATTINY microcontroller. MIDI signals are received at TTL voltage levels, and converted to output voltages by the ATTINY via use of the PWM hardware. A lowpass filter is added to remove the high-frequency content from the output signal.  A 6N138 optocoupler completes the project, to comply with the MIDI standard and ensure the device is not subject to any dangerous voltages from the hardware plugged in.

It’s a simple way to control older non-MIDI compliant hardware, and might make an old modular rig just that much more useful in the studio of today. We’ve seen similar builds before, like this combined CV and Gate converter. 

Open Source Fader Bank Modulates Our Hearts

Here at Hackaday, we love knobs and buttons. So what could be better than one button? How about 16! No deep philosophy about the true nature of Making here; [infovore], [tehn], and [shellfritsch] put together a very slick, very adaptable bank of 16 analog faders for controlling music synthesis. If you don’t recognize those names it might help to mention that [tehn] is one of the folks behind monome, a company built on their iconic grid controller. Monome now produces a variety of lovingly crafted music creation tools.

Over the years we’ve written about some of the many clones and DIY versions of the monome grid controller, so it’s exciting to see an open source hardware release by the creators themselves!

The unambiguously named 16n follows in the footsteps of the monome grid in the sense that it’s not really for something specific. The grid is a musical instrument insofar as it can be connected to a computer (or a modular synth, etc) and used as a control input for another tool that creates sound. Likewise, the 16n is designed to be easily integrated into a music creation workflow. It can speak a variety of interfaces, like purely analog control voltage (it has one jack per fader), or i2c to connect to certain other monome devices like Ansible and Teletype. Under the hood, the 16n is actually a Teensy, so it’s fluent in MIDI over USB and nearly anything else you can imagine.

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MIDI To CV/Gate The Easy Way

Let’s say you’ve got a modular synthesizer. You’re probably a pretty cool person. But all your cool laptop DJ friends keep showing off their MIDI-controlled hardware, and you’re getting jealous. Well, [little-scale] has the build for you.

The Teensy 3.6 is the current top-of-the-line Teensy from PJRC, and it’s [little-scale]’s weapon of choice here. With USB-MIDI and two 12-bit DACs on board, it’s made creating an interface between the worlds of analog and digital music into a remarkably simple job. Control voltages for pitch and velocity are pushed out over the analog pins, while pin 29 is used for gate signals.

It’s a testament to the amount of development that has gone into the Teensy platform that such projects can be built with virtually no off-board components. The build is a further step forward in simplicity from [little-scale]’s previous work, using a Teensy 2 with an offboard DAC to generate the output voltages.

Here at Hackaday, we’ve always been big fans of adding computer control to analog hardware. This CNC mod to a guitar pickup winding machine is a great example.

IPad Control For Guitar Pedals

[gutbag] is a guitarist. And guitarists are notorious knob-twiddlers: they love their effects pedals. But when your music involves changing settings more than a few times in the middle of a song, it can get distracting. If only there were little robot hands that could turn the knobs (metaphorically, sorry) during the performance…

Tearing into his EHX Pitch Fork pedal, [gutbag] discovered that all of the external knob controls were being read by ADCs on the chip that did all of the processing. He replaced all of the controls with a DAC and some analog switches, coded up some MIDI logic in an ATmega328, and built himself a custom MIDI-controlled guitar pedal. Pretty slick, and he can now control it live with his iPad, or sequence the knobs with the rest of their MIDI system.


This wasn’t [gutbag]’s first foray into pedal automation, however. He’d previously automated a slew of his pedals that were already built to take control-voltage signals. What we like about this hack is the direct substitution of DAC for potentiometers. It’s just hackier. (Oh, and we’re envious of [gutbag]’s lab setup.)

This isn’t the first time we’ve covered [gutbag]’s band, Zaardvark, either. Way back in 2013, we featured an organ-pedal-to-MIDI hack of theirs. Keep on rockin’.

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Busted Wah Pedal Becomes New Synth Tool

Sometimes we get lucky and find a part we need for a project in our parts drawer. [Scissorfeind] got even luckier and found a part for his project lying around in the street. It was a Crybaby Wah pedal, a classic effects pedal typically used for a guitar. Since it was somewhat damaged, [Scissorfeind] got to work creating a control voltage (CV) and volume circuit for his Korg synthesizer.

For those who aren’t synthesizer aficionados, CV is a method of controlling the pitch of a tone. A higher voltage creates a higher tone and vice-versa. The wah pedal has a rocker on it that allows one’s foot to control the effect, but this particular one has been modified for CV instead of the wah-wah sound these pedals normally make. [Scissorfeind] built in a switch that will allow it to control volume as well, which makes this pedal quite unique in the effects world.

[Scissorfeind] built the custom circuit out of other parts he had lying around (presumably not in the street) and put the entire thing together on perfboard, then fit it all back together in the pedal. Now he has a great control voltage pedal for the vintage Korg synthesizer he recently restored! [Scissorfeind] knows his way around a synth, but if you’re looking to get started on a synthesizer project we have a great tutorial for you!