Making An ARM Powered MIDI Synthesizer

What you see in the picture above is a hand-made 4-oscillator synthesizer with MIDI input, multi-mode filter and a handful of modulation options. It was built by [Matt], an AVR accustomed electronics enthusiast who made an exception to his habits for this project. The core of the platform is a DIP packaged 32-bit Cortex-M0 ARM processor (LPC1114), stuffed with ‘hand’ written assembly code and compiled C functions. With a 50MHz clock speed, the microcontroller can output samples at 250kHz on the 12bit DAC while being powered by 3 AA batteries.

Reading [Matt]’s write-up, we discover that the firmware he created uses 4 oscillators (sawtooth or pulse shape) together with a low frequency oscillator (triangle, ramp, square, random shapes). It also includes a 2-pole state-variable filter and the ability to adjust the attack-release envelopes (among others). The system takes MIDI commands from a connected device. We embedded videos of his creation in action after the break.

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Piano Repurposed as a Resonant Synth Speaker


[Richard] recently rediscovered some files from a hack he did back in 2004. He was experimenting with exciting piano strings via electromagnetic fields. The idea shares some elements with the self tuning piano we saw back in 2012. Piano strings, much like guitar strings, are made of steel alloys. This means they create electricity when vibrated in a magnetic field. This is the basic principle upon which electric guitar pickups are built. The idea also works in reverse. The strings will vibrate in response to a modulated electromagnetic field. Anyone who has seen an E-bow knows how this can be applied to the guitar. What about the piano?

[Richard] started with the Casio CZ-101, a classic synth in its own right. The Casio’s output was run through a Peavy 100 watt amplifier. The amplified output was then used to drive custom coils mounted on a piano. The coils had to be custom wound to ensure they would be compatible with the 4 – 8 ohm impedance expected by the amplifier. [Richard] ended up winding the coils to 28 ohms. Six of these coils in parallel put him just over the 4 ohm mark. The coils effectively turned the piano into a giant speaker for the synth. In [Richard’s] write-up (word doc link) he mentions that the strings basically act as a giant comb filter, each resonating strongly in response to frequencies in its harmonic series.

The results are rather interesting. The slow attack of the magnetic fields coupled with the synth’s patch results in a surprising variety of sound. The three examples on [Richard’s] blog vary from sounding like a power chord on a guitar to something we’d expect to find in an early horror movie. We would love to see this idea expanded upon. More efficient coils, and more coils in general would add to the effect. The coils on various string groups could also be switched in and out of the system using MIDI control, allowing for even more flexibility. Continue reading “Piano Repurposed as a Resonant Synth Speaker”

Keyboard Spoofs 4 NES Controllers for Chiptune Goodness


This toy keyboard is being used to play music on an NES. As you probably already know, the hardware inside those original controllers was dead simple. They’re just a parallel to serial shift register that reads from all of the keys. To get this keyboard up and running [heavyw8bit] simply mounted eight chips inside the gutted toy, connecting two of them to the keyboard keys, and the rest to the array of push buttons he added to the right.

So what’s the point of using this as a quadruple game controller? Are you expecting to see what a full speed-run of Contra looks like using this as the controls? That’s not the point at all. This becomes a musician-friendly frontend for the NES synthesizer ROM called NESK-1. [heavyw8bit] wrote the game/program in order to allow you to use the original console hardware to play all of the sounds you know and love. Our favorite is the arpeggio example heard at about 2:35 into the clip after the break.

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Retrotechtacular: Discovering Electronic Music


We take it for granted today that a lot of the music we hear includes synthesized instruments and sounds. But looking all the way back to 1983 for this Discovering Electronic Music video series provides a glimpse of the humble beginnings of the technology. The first five minutes of part one may annoy your aurally, but it’s worth it as that’s the point at which we get into sound generation using equipment like that seen above. All three parts in the series are embedded below; about twenty minutes of video in total.

Mixer boards and other control interfaces used today still have a large area of real estate devoted to knobs and adjustments. But they also include a ton of software processing options which weren’t available until computers became both affordable and ubiquitous. What’s shown in the video is a set of hardware interfaces that process signals from oscillators or alter recorded sound. We’ve spent a lot of time marveling about software defined radio and how it’s making RF hacking accessible to the masses. But who here hasn’t done at least a bit of tinkering in electronic music using any of the myriad of audio software? Would you have done that if you needed to build your own envelope and filter circuitry?

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Time-lapse synthesizer build will blow your mind

[themonkeybars] recently uploaded a time-lapse video of his DIY synthesizer build. First off the video itself is a pretty neat hack. An iPhone time-lapse app was used to capture one frame every 5 seconds. By the time the build was complete, approximately 46,000 frames had been snapped. This boiled down to over 43 minutes of youtube footage. [themonkeybars] didn’t work full time on the project, so the video covers about a year’s worth of work which we think makes it even cooler. The synth is also featured in much of the video’s soundtrack.

The synthesizer itself would be classified as an analog modular synth, a type we’ve seen before. Modular synthesizers are one of the earlier forms of electronic music. The synthesizer is composed of discrete modules such as oscillators, modulators, and filters. The modules may be housed in the same box, but they are not internally connected. All connections are made via front panel patch cables. This is where the term “Patch” came from. Continue reading “Time-lapse synthesizer build will blow your mind”

Pair of MIDI dongles to inspire some weekend music hacking


This pair of dongles is a fun way to get your feet wet working with MIDI hardware. They’re called MIDIvampire-I and MIDIvampire-II. Just plug one end into your MIDI-ready instrument and the other into a pair of speakers and you’re off and running. Mark I is a polyphonic synth, and Mark II is a drum machine, but both use basically the same hardware which you may already have on hand.

The single chip on each board is an ATmega328 often found anchoring Arduino boards. The other silicon component is an S1112B30MC voltage regulator. The rest of the components are passives, with MIDI and headphone jacks for connectivity. They’re selling these if you want the easy way out, but we thought we’d bring them to your attention in case you needed a breadboarding project this weekend. The firmware, BOM, schematic, and board artwork are all available on the Wiki pages linked in the articles above. After the break you can see a couple of demo videos which walk through all of the features.

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Turning a tiny Linux box into a synthesizer


For all the cool things the Raspberry Pi, BeagleBone, and other low-power Linux boards can do, there’s one thing we haven’t seen much of: creating music with software synthesizers. Yes, soft synths have been around for ages now, but compiling them for these ARM boards is something we haven’t seen much of (to say nothing of the Linux audio system). Luckily, [Paul] and [Trev] have put together a tutorial for making synthesizers on these small Linux boards using Csound, the premier audio programming language for Linux.

[Paul] and [Trev] have already put together a few Csound instruments that include a Vangelis-inspired synth, a Lorenz Strange Attractor FM synth, a drum machine, and a classic monophonic style synth. All these instruments are ready to play on a Raspi or BeagleBone and we’re sure we’ll see a few more applications of this great tool for creating musical instruments as more musicians are turned onto these small Linux boards.