midi

374 Articles

OpenMIDIStomper Makes Sure Your Gear Does What Your Foot Says

July 3, 2025 by 1 Comment

If you’re a solo musician, you probably have lots of gear you’d like to control, but you don’t have enough hands. You can enlist your feet, but your gear might not have foot-suitable interfaces as standard. For situations like these, [Nerd Musician] created the OpenMIDIStomper.

The concept is simple enough—the hardy Hammond enclosure contains a bunch of foot switches and ports for external expression pedals. These are all read by an Arduino Pro Micro, which is responsible for turning these inputs into distinct MIDI outputs to control outboard gear or software. It handles this via MIDI over USB. The MIDI commands sent for each button can be configured via a webpage. Once you’ve defined all the messages you want to send, you can export your configuration from the webpage by cutting and pasting it into the Arduino IDE and flashing it to the device itself.

We’ve featured some great MIDI controllers over the years, like this impressive parts bin build.

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A black PCB is shown, with an Arduino Nano mounted in the bottom left corner. The rest of the space on the PCB is used up by ten DIP integrated circuits and a few resistors and diodes. Several black and red wires connect different parts of the PCB.

Meowsic Keyboard MIDI Adapter Aims For Purrfection

June 14, 2025 by 3 Comments

Both small children and cats have a certain tendency to make loud noises at inopportune times, but what if there were a way to combine these auditory effects? This seems to have been the reasoning behind the creation of the Meowsic keyboard, a children’s keyboard that renders notes as cats’ meows. [Steve Gilissen], an appreciator of unusual electronic instruments, discovered that while there had been projects that turned the Meowsic keyboard into a MIDI output device, no one had yet added MIDI input to it, which of course spurred the creation of his Meowsic MIDI adapter.

The switches in the keys of the original keyboard form a matrix of rows and columns, so that creating a connection between a particular row and column plays a certain note. [Steve]’s plan was to have a microcontroller read MIDI input, then connect the appropriate row and column to play the desired note. The first step was to use a small length of wire to connect rows and columns, thus manually mapping connections to notes. After this tedious step, he designed a PCB that hosts an Arduino Nano to accept input, two MCP23017 GPIO expanders to give it enough outputs, and CD4066BE CMOS switches to trigger the connections.
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When Wireless MIDI Has Latency, A Hardwired Solution Saves The Day

June 7, 2025 by 14 Comments

[Moby Pixel] wanted to build a fun MIDI controller. In the end, he didn’t build it just once, but twice—with the aim of finding out which microcontroller was most fit for this musical purpose. Pitted against each other? The ESP32 and Raspberry Pi Pico.

The MIDI controller itself is quite fetching. It’s built with a 4 x 4 array of arcade buttons to act as triggers for MIDI notes or events. They’re assembled in a nice wooden case with a lovely graphic wrap on it. The buttons themselves are wired to a microcontroller, which is then responsible for sending MIDI data to other devices.

At this point, the project diverges. Originally, [Moby Pixel] set the device up to work with an ESP32 using wireless MIDI over Bluetooth. However, he soon found a problem. Musical performance is all about timing, and the ESP32 setup was struggling with intermittent latency spikes that would ruin the performance. Enter the Raspberry Pi Pico using MIDI over USB. The hardwired solution eliminated the latency problems and made the controller far more satisfying to use.

There may be solutions to the latency issue with the wireless ESP32 setup, be they in code, hardware configuration, or otherwise. But if you want to play with the most accuracy and the minimum fuss, you’ll probably prefer the hardwired setup.

Latency is a vibe killer in music as we’ve explored previously.

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It’s MIDI For The TRS-80!

June 1, 2025 by 16 Comments

The Radio Shack TRS-80 was a much-loved machine across America. However, one thing it lacked was MIDI. That’s not so strange given the era it was released in, of course. Nevertheless, [Michael Wessel] has seen fit to correct this by creating the MIDI/80—a soundcard and MIDI interface for this old-school beast.

The core of the build is a BluePill STM32F103C8T6 microcontroller, running at a mighty 75 MHz. Plugged into the TRS-80s expansion port, the microcontroller is responsible for talking to the computer and translating incoming and outgoing MIDI signals as needed. Naturally, you can equip it with full-size classic DIN sockets for MIDI IN and MIDI OUT using an Adafruit breakout module. None of that MIDI Thru nonsense, though, that just makes people uncomfortable. The card is fully capable of reproducing General MIDI sounds, too, either via plugging in a Waveblaster sound module to the relevant header, or by hooking up a Roland Sound Canvas or similar to the MIDI/80s MIDI Out socket. Software-wise, there’s already a whole MIDI ecosystem developing around this new hardware. There’s a TRS-80 drum tracker and a synthesizer program, all with demo songs included. Compatibility wise, The MIDI/80 works with the TRS-80 Model I, III, and 4.

Does this mean the TRS-80 will become a new darling of the tracker and chiptune communities? We can only hope so! Meanwhile, if you want more background on this famous machine, we’ve looked into that, too. Video after the break.

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Zen Flute Is A Teensy Powered Mouth Theremin

May 17, 2025 by 13 Comments

An intriguing mouth-played instrument emerged—and won—at the 2023 Guthman Musical Instrument Contest hosted by Georgia Tech. [Keith Baxter] took notice and reproduced the idea for others to explore. The result is the Zen Flute Mouth Theremin, a hybrid of acoustics, electronics, and expressive performance.

At its core lies a forced Helmholtz resonator, a feedback system built with a simple microphone and speaker setup. The resonator itself? The user’s mouth. The resulting pitch, shaped by subtle jaw and tongue movements, is detected and used to drive a MIDI controller feeding an external synthesizer.

Like a trombone or classic electromagnetic theremin, the Zen Flute doesn’t rely on discrete notes. Instead, the pitch is bent manually to the desired frequency. That’s great for expression, but traditional MIDI quantisation can map those “in-between” notes to unexpected semitones. The solution? MIDI Polyphonic Expression (MPE). This newer MIDI extension allows smooth pitch transitions and nuanced control, giving the Zen Flute its expressive character without the hiccups.

Physically, it’s an elegant build. A flat speaker and microphone sit side-by-side at the mouth end, acoustically isolated with a custom silicone insert. This assembly connects to a length of clear PVC pipe, flared slightly to resemble a wind instrument. Inside, a custom PCB (schematic here) hosts a mic preamp, an audio power amp, and a Teensy 4.1. The Teensy handles everything: sampling the mic input, generating a 90-degree phase shift, and feeding it back to the speaker to maintain resonance. It also detects the resonant frequency and translates it to MPE over USB.  A push-button triggers note onset, while a joystick adjusts timbre and selects modes. Different instrument profiles can be pre-programmed and toggled with a joystick click, each mapped to separate MIDI channels.

Mouth-controlled instruments are a fascinating corner of experimental interfaces. They remind us of this Hackaday Prize entry from 2018, this wind-MIDI hybrid controller, and, of course, a classic final project from the Cornell ECE4760 course, a four-voice theremin controlled by IR sensors.

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Laser Harp Sets The Tone

March 20, 2025 by 16 Comments

In many ways, living here in the future is quite exiting. We have access to the world’s information instantaneously and can get plenty of exciting tools and hardware delivered to our homes in ways that people in the past with only a Sears catalog could only dream of. Lasers are of course among the exciting hardware available, which can be purchased with extremely high power levels. Provided the proper safety precautions are taken, that can lead to some interesting builds like this laser harp which uses a 3W laser for its strings.

[Cybercraftics]’ musical instrument is using a single laser to generate seven harp strings, using a fast stepper motor to rotate a mirror to precise locations, generating the effect via persistence of vision. Although he originally planned to use one Arduino for this project, the precise timing needed to keep the strings in the right place was getting corrupted by adding MIDI and the other musical parts to the project, so he split those out to a second Arduino.

Although his first prototype worked, he did have to experiment with the sensors used to detect his hand position on the instrument quite a bit before getting good results. This is where the higher power laser came into play, as the lower-powered ones weren’t quite bright enough. He also uses a pair of white gloves which help illuminate a blocked laser. With most of the issues ironed out, [Cybercraftics] notes that there’s room for improvement but still has a working instrument that seems like a blast to play. If you’re still stuck in the past without easy access to lasers, though, it’s worth noting that there are plenty of other ways to build futuristic instruments as well.

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Shellcode Over MIDI? Bad Apple On A PSR-E433, Kinda

January 23, 2025 by 6 Comments

If hacking on consumer hardware is about figuring out what it can do, and pushing it in directions that the manufacturer never dared to dream, then this is a very fine hack indeed. [Portasynthica3] takes on the Yamaha PSR-E433, a cheap beginner keyboard, discovers a shell baked into it, and takes it from there.

[Portasynthinca3] reverse engineered the firmware, wrote shellcode for the device, embedded the escape in a MIDI note stream, and even ended up writing some simple LCD driver software totally decent refresh rate on the dot-matrix display, all to support the lofty goal of displaying arbitrary graphics on the keyboard’s dot-matrix character display.

Now, we want you to be prepared for a low-res video extravaganza here. You might have to squint a bit to make out what’s going on in the video, but keep in mind that it’s being sent over a music data protocol from the 1980s, running at 31.25 kbps, displayed in the custom character RAM of an LCD.

As always, the hack starts with research. Identifying the microcontroller CPU lead to JTAG and OpenOCD. (We love the technique of looking at the draw on a bench power meter to determine if the chip is responding to pause commands.) Dumping the code and tossing it into Ghidra lead to the unexpected discovery that Yamaha had put a live shell in the device that communicates over MIDI, presumably for testing and development purposes. This shell had PEEK and POKE, which meant that OpenOCD could go sit back on the shelf. Poking “Hello World” into some free RAM space over MIDI sysex was the first proof-of-concept.

The final hack to get video up and running was to dig deep into the custom character-generation RAM, write some code to disable the normal character display, and then fool the CPU into calling this code instead of the shell, in order to increase the update rate. All of this for a thin slice of Bad Apple over MIDI, but more importantly, for the glory. And this hack is glorious! Go check it out in full.

MIDI is entirely hacker friendly, and it’s likely you can hack together a musical controller that would wow your audience just with stuff in your junk box. If you’re at all into music, and you’ve never built your own MIDI devices, you have your weekend project.

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