Musical Hacks

1512 Articles

This Handy Synth Packs An ESP32

May 2, 2026 by 8 Comments

Since the first electronic hobbyist wired up a multivibrator to a keyboard many decades ago, electonic synthesisers have been a staple of home-made projects. Now with the proliferation of significantly powerful microcontrollers it’s possible to make a synth that surpasses many of the high-end models from days gone by.

Among those we’ve seen of late perhaps none does this better than [Povle] with their Spark portable keyboard. It’s a tiny thing that reminds us of those little Casio synths of the 1980s, but in its 3D printed case it packs a load of features.

Hardware wise it’s an ESP32 with a 3D printed keyboard using keyswitches. There are a load of pots for sound adjustment, and buttons for functions. A small OLED display shows what’s going on. Software wise it relies upon the AMY synth library, and there are repositories for both its hardware and software.

There’s a demo video we’ve placed below, and in it you hear the keyboard at work. And here maybe we’ve saved the best until last, because alongside being a fully featured synth, it’s also a sampler and a Bluetooth MIDI keyboard. Is there nothing this thing can’t do!

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ESP32Synth : An Audio Synthesis Library For The ESP32

April 23, 2026 by 11 Comments

With MCUs becoming increasingly more powerful it was only a matter of time before they would enable some more serious audio-processing tasks. [Danilo Gabriel]’s ESP32Synth library is a good example here, which provides an ESP-IDF based 80+ voice mixing and synthesis engine. If you ever wanted to create a pretty impressive audio synthesizer, then all you really need to get started is an ESP32, ESP32-S3 or similar dual-core Espressif MCU that has the requisite processing power.

Audio output goes via I2S, requiring only a cheap I2S DAC like the UDA1334A or PCM5102 to be connected, unless you really want to use the internal DAC. With this wired up you get 80 voices by default, with up to 350 voices demonstrated before the hardware cannot keep up any more. You can stream multiple WAV files from an SD card for samples along with the typical oscillators like sinewave, triangle, sawtooth and pulse, as well as noise, wavetables and more.

In order to make this work in real-time a number of optimizations had to be performed, such as the removal of slow floating-point and division operations in the audio path. The audio rendering task is naturally pinned to a single core, leaving a single core for application code to use for remaining tasks. While the code is provided as an Arduino project, it uses ESP-IDF so it can likely be used for a regular ESP-IDF project as well without too much fuss.

Wearable MIDI Controller Built With Raspberry Pi

April 21, 2026 by 7 Comments

Most synths happily get by with keyboard or pad inputs and make lovely sounds in response. [Becky Clarke] and her fellow collaborators are building a synth that works rather differently. DigitSynth is a wearable controller that’s rather fun to interact with.

The heart of the build is a Raspberry Pi 5. It’s set up to talk to a TI ADS1115 ADC chip that lets it read a bunch of analog flex sensors embedded in a right-hand glove, while the Pi can also read a bunch of tactile buttons activated by the left hand. The flex sensors are used to control synth parameters like LFO rate and filter cutoffs, while the buttons control chord changes. The Raspberry Pi runs custom code to read these devices and generate the requisite MIDI commands to send to a Roland JD-Xi synth which is responsible for actually making the sound. Both sets of fingers are also dotted with LEDs for visual feedback, controlled via a TLC59711 PWM driver.

It’s a fun build that creates some ethereal sounds in an intuitive way, thanks to the nature of the interface. We’ve featured some similar builds before, using the flexure of the hand to create musical soundscapes. Video after the break.

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DJ Controller Modded For Better Scratching

April 18, 2026 by 4 Comments

[Jeremy Bell] loves scratching, but he had a problem. His Hercules DJ controller wasn’t really doing a great job at emulating the kind of action one would get with a real turntable. The solution was both mechanical and electronic in nature!

As stock, the Hercules MIDI rig lets you scratch in a relatively simplistic way. When it detects a finger touching the rotary control, it lets you scratch back and forth with great motion tracking. However, when you let go, playback resumes at regular speed instantaneously, which creates a somewhat inorganic sound.

The fix was to make some mechanical mods to the MIDI controller. [Jeremy] tried out a variety of different methods of using a motor to spin the rotary control continuously, from geared rigs to belt-driven setups. It was then possible to scratch on the controller, and then let it return to normal rotational speed, creating much smoother  auditory transitions. However, this was imperfect, as for whatever reason, the Hercules rig would stop tracking the rotary control accurately unless it detected a finger was touching it. [Jeremy] worked around this by whipping up a slip-ring-like setup to keep his body permanently in contact with the rotary control even while spinning.

The results are pretty great—they’re both mechanically janky and fantastically satisfying to listen to. We’ve featured some other great DJ controller hacks over the years, like this sweet Pioneer UI upgrade.

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Audio Reactive LED Strips Are Hard

April 14, 2026 by 16 Comments

Back in 2017, Hackaday featured an audio reactive LED strip project from [Scott Lawson], that has over the years become an extremely popular choice for the party animals among us. We’re fascinated to read his retrospective analysis of the project, in which he looks at how it works in detail and explains that why for all its success, he’s still not satisfied with it.

Sound-to-light systems have been a staple of electronics for many decades, and have progressed from simple volume-based flashers and sequencers to complex DSP-driven affairs like his project. It’s particularly interesting to be reminded that the problem faced by the designer of such a system involves interfacing with human perception rather than making a pretty light show, and in that context it becomes more important to understand how humans perceive sound and light rather than to simply dump a visualization to the LEDs. We receive an introduction to some of the techniques used in speech recognition, because our brains are optimized to recognize activity in the speech frequency range, and in how humans register light intensity.

For all this sophistication and the impressive results it improves though, he’s not ready to call it complete. Making it work well with all musical genres is a challenge, as is that elusive human foot-tapping factor. He talks about using a neural network trained using accelerometer data from people listening to music, which can only be described as an exciting prospect. We genuinely look forward to seeing future versions of this project. Meanwhile if you’re curious, you can head back to 2017 and see our original coverage.

The omatraumatone. Or something. It's a synth.

Otamatone Hacked Into Different, Cooler Synth: Trautonium

April 10, 2026 by 8 Comments

Analog synths are fun because they combine music, which all humans seem hard-wired to enjoy in one form or another, and electronics, which… uh, this is Hackaday. If you don’t like electronics, we’re not sure what to tell you. This hack from [Sound Workshop] takes the cheap, toy-like Otamatone and turns it into an older and more capable type of synthesizer: a Trautonium. The video below also includes a dive into the different types of early synthesizers, with examples of them playing, so it’s worth watching for that alone — if you know the history, skip the first five minutes or so.

For those of you more into the electronics than the music side of things, the Otamatone is kind of like an electronic slide whistle, but adorable. Shaped like an eighth note or a tadpole, you control pitch by sliding your fingers up and down the ‘tail’ and activate the voice by squeezing the ‘head’ to open the mouth. It is one of the newest electronic instruments on the market, having debuted as a Japanese toy in 2009.

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The Rapper, The Canadian Academics, And The Secret Behind The Earworm

April 4, 2026 by 13 Comments

There are many events so far in 2026 that could reasonably have been predicted, but perhaps one which couldn’t is a Hackaday scribe in Europe unexpectedly finding herself with a constant earworm from Afroman. The rapper, who most of us know only from his year 2000 hit single about getting high, made the news after an inept police raid on his house, and in turn a court case over his musical denunciations of the authorities.

It’s fair to say they picked on the wrong guy, but in thinking about why, the answer is in the earworm. He has the unique skill of making a song irritatingly catchy, which led us to the question of how a catchy song works. As luck would have it a team from the University of Waterloo have recently released a paper in which they explain  it all in terms of maths, giving the rest of us a formula where the likes of Afroman are presumably born with it.

We won’t pretend that Hackaday’s mathematical expertise stretches beyond that needed for engineering, but for the more advanced numberphiles among us the university’s write-up goes into some detail about their use of group theory to study the patterns and symmetry in a given piece of music. It’s a new approach that joins other more famous guides to musical success, so perhaps if you couple it with the stuff your music teacher failed to tell you in school, you could be on your way to the top of the charts. Meanwhile here at Hackaday we’ll stick to more conventional inspiration.

Header: Chris Gilmore, CC BY-SA 2.0.