If you’d like a pseudo-mechanical way of producing a droning synthesizer sound, [gijs] is your man. He made a small synthesizer out of nothing but an old hard drive and a few components.

Whenever a disk platter is spun manually, the spindle motor inside the drive produces a few out of phase sine waves on its connections. [gijs]‘ synthesizer compares and amplifies these sine waves and sends them out to a speaker. The result is a strange droning chiptune-esque arpeggio.

The circuit for the build is soldered directly to the hard drive enclosure Manhattan style. Because the output of the spindle motor produces out of phase sine waves, [gijs] thought it would be a good idea if he could capitalize on some phase interference to alter the timbre of his synth. The entire build is mounted to a wall with hinges to one side so the speaker can be moved around. It isn’t much of a change, but we can here some wave forms cancelling each other out.

Check out the video of the build after the break. There’s also a few audio samples available on the project page.

Chiptunes are great, and we can’t imagine a world without the Mega Man 2 soundtrack, but sometimes we all like a more 70′s style synth. This is where the Roninsynth steps in. It’s an Arduino shield that puts the basic components of a wall of synth into your pocket.

Unlike the analog oscillators of yore, the Roninsynth is based on a single dsPIC33F chip. It has all the waveforms we would expect from its big brother – sine, saw, triangle, square, and noise – and a couple modulation options.  What’s really interesting is the GUI the Roninsynth team put together. Instead of going with the knobs and buttons approach of the MIDIbox SID, the Roninsynth does everything with software. Think of it as a hardware-based softsynth.

Of course, there isn’t support for looping and phrases like what we saw yesterday, but there’s a ton of neat sounds that can be made and the capability for analog input. If you’ve ever wanted to sound like Radiohead, we can’t think of an easier way to build an Ondes Martenot.

Wow. And furthermore, WOW! Just looking at that clean prototype you know that a lot of work has gone into the project, but when you hear this chiptune MIDI device you’ll really be impressed. We know what you’re thinking, but really, you’ve got to hear this to appreciate the quality [Linus Akesson] achieved in this synthesizer. You can catch it after the break.

He does a great job of showing off the different waveforms that can be produced by the ATmega88 on this board. But there’s much more. It also serves as a 16 frame, 16 channel sequencer for creating and layering your own loops.

He mentions that eight oscillators are used for the waveform generation. We don’t see hardware for this on the board. Either we’re missing it, or these oscillators are being created with software? If you have an idea of how this works please clue us in by leaving a comment.

[Thanks 7e]

There’s a million and one ways to play around with MIDI and an Arduino. It’s trivial to have a ‘duino spit out a scale to a MIDI keyboard, or even respond to SysEx messages to change a lighting or effects rig. There’s one thing that has eluded MIDI-duino builders, though: implementing a MIDI synthesizer with a DIY shield. It’s a good thing, then, that [Keith] put up a Kickstarter for his AvecSynth project.

[Keith]‘s AvecSynth is based around the Dream.fr SAM2195 single chip MIDI synthesizer. It’s a neat little IC that takes in MIDI messages from a sequencer or keyboard and spits out stereo audio. The AvecSynth takes this IC and puts it in a standard Arduino-sized package so building a gigantic light-up, foot-operated piano is now well within the purview of the weekend solder junkie.

While the SAM2195 and AvecSynth doesn’t have fancy subtractive or FM synthesis, it does have the full set of 128 voices in the General MIDI spec. It’s a great project to play around with MIDI, and the price for the DIY kit is right up our alley.

EDIT: [Keith] changed the $20 reward for his Kickstarter to PCB or two SAM2195 chips

[Charles Gershom] has been tinkering around with his keyboard and Arduino in order to build his own version of a MIDI controlled synthesizer. It looks like he’s gutted the enclosure of some commercially available MIDI hardware to use for the project. This works nicely since it gives him both the MIDI and audio jacks that he needs. The box also provides a nice control surface where a set of four LEDs indicates the synth mode currently in use. There are also four potentiometers mounted on the panel, but they’re not yet up and running.

Check out the video after the break to see what this can do so far. [Charles] shows the device synthesizing sounds coming in from the keyboard. It is also used to playback the audio from Super Mario Bros. which is fed in by a music notation program on a computer. Only one voice is playing when this happens which makes us think this can only handle one channel at a time right now (but we could be wrong).

[74hc595] just finished his entry in the 7400 logic contest. It’s a drum machine built entirely from 7400-series logic chips. He hasn’t quite reached full completion of the project yet. The hardware works just fine, and he’s built a foam core face plate with many more controls than you see here but much of the circuit is still on a breadboard at this point and only two of the channels have been complete thus far.

Jump to the video clip after the break to get the details of how the system works and to hear it in action. This demonstration is one of the best we’ve seen for a synthesizer project as he actually talks about what each control does, and how that is accomplished with the hardware. We’re not going to go into detail about the circuitry he’s designed. As we said before, it uses 7400 logic but also sources a 555 timer to keep the beat. The page linked above has a PDF of the schematic available and you could really lose a lot of time studying how he did this. We might even try to build it in a simulator to see what we can learn.

[Dirk] let us know about this fantastic music synthesis experimentation setup (translated). Turn your computer speakers off (to avoid the auto-playing music when every page loads) and dig into the wealth of information in this repository. Literally dozens of modules have been built and superbly mounted on a rack system. Each can be connected with other modules into an incredible number of different setups using patch wires that terminate with banana plugs.

The module enclosures themselves are made to fit in a standard 19″ rack. The front bezels were designed in CAD, with the rest of the housing made mostly of aluminum. Since each module tends to be quite small several are ganged into one rack skeleton to save space. You can see in the images above that there are as many as eight modules per rack slice.

You’ll enjoy reading about the many different sound chips that are in use here. But it doesn’t have to end there. If this has whet your appetite for your own rack-mounted system you’re in luck. The download area has schematics, board artwork, and build information for most of the modules.

We always like musical hacks at hackaday, so we were pleased to see the team at [Beat707] come out with their Beat707 MIDI groove box.

The Beat707 takes it’s inspiration from the venerable Roland TR-707. Like the Roland, the Beat707 can save songs and has MIDI In and Out. Unlike the TR-707, the Beat707 doesn’t have an audio out – it’s purely MIDI based. Don’t think of that as a drawback, though. Just connect the Beat707 to your favorite softsynth and start jamming out.

The Roland TR-707 was heavily used by acts like the Chemical Brothers, Aphex Twin, and the Cocteau Twins. Because of this history, the popularity of the TR-707 has exploded over the past few years, and getting a hold of a real TR-707 has been an expensive proposition. While rebuilds of vintage synths like [Ladyada]‘s TB-303 clone, the x0xb0x have been around for a while, we’re pleased that more projects are paying their dues to the great music machines of the 1980s.  Do any hackaday readers want to tackle an 808 or 909 for their next project?

Video of the Beat707 after the break.

[Jeremy Blum] recently finished writing a couple of software packages for his SudoGlove system that turns it into a music controller with a lot of features. We’ve seen the hardware in a previous post and as a goal for this iteration he decided not to alter the hardware or the firmware controlling it whatsoever–making this a PC-side software only hack. It’s nice to see improvement on the original ideas as we feel most of the glove-based projects we’ve covered end up getting thrown in the junk box after the developer’s interest wanes.

After the break you can see and hear a demonstration of the complete system. The front end of application shown was written using Processing and includes a slew of user configurations for each sensor on the glove itself. Under the hood [Jeremy] built on the PureData framework in order to really unlock the potential for translating physical movement into synthesized sound. There is also a visual feedback application which will help you practice your movements, important if you’re giving live performances where each finger is a different instrument. Everything for this project, both hardware and software, has been released under a CC license so check out [Jeremy's] site if you’re interested in building on part or all of the good work he’s done.

Update: [Jeremy] wrote in with a bit of a correction for our synopsis. The application shown in the video is written entirely in PureData and the visual debugger was written with Processing. The two are standalone packages that don’t depend on each other. He also sent us a link to download the code packages.

[Derek Enos'] toils are starting to yield results. He’s been working on an 8-bit synthesizer that is MIDI controlled which he calls the deMIDulator. As he demonstrates after the break, the device has sine and square wave functions that produce quite a pleasing sound. But it also offers the option to record your own samples which are then modified based on the MIDI commands coming in from your device of choice. In this case he’s using a Rock Band 3 keyboard (or keytar if you will) in a much more creative way than its originally intended purpose.

For now we’ll have to be content with the demo video and a list of features as there are no other details. But open sourcing the code and hardware information are on his to-do list.

Electronic musical instruments are a lot of fun for a hacker because, with a small palette of tools, know-how and curiosity, they are easily modified. As with any hack, there is always the chance that the subject will be ruined, so it’s not necessarily worth the risk to muck about inside your thousand-dollar pro synthesizer. Luckily for all of us, there are shovel-fulls of old electronic musical toys littering the curbs and second-hand shops of the world. These fun little devices provide ample opportunity to get familiar with audio electronics and circuit bending techniques.

A note on definitions: the term “circuit bending” can be synonymous with “hardware hacking” in the world of audio electronics, and we have seen some debate as to which term is better suited to a given project. We welcome you to share your viewpoints in the comments.

Keep reading to get started.

Materials

So, you’ve heard of circuit bending and you want to give it a try eh? Well for this introduction, you’re going to need at minimum the following materials:

• electronic musical instrument (the bendee) with batteries or AC adapter
• alligator clips (for temporary connections)
• various resistors and/or a potentiometer
• ears

and it’s a great help if you also have:

• oscilloscope
• bench-top power supply
• camera

For our first attempt at circuit bending, we will be using a Yamaha PSS-14 keyboard. We found it by the side of the road, abandoned and lonely and without a friend in the world. Like mad scientists conducting mad genetic experiments on lonely abandoned animals, we will rebuild this poor creature to be better, stronger, and stranger than before!

Background Research

Thanks to our high-fallootin’ academic standards, we’ll start by researching a little bit about the keyboard in question. The more adventurous among you can skip this step and dive straight into the fun part. From Yamaha’s site, we can see that this model sports “100 Advanced Wave Memory Voices”–that’s their hilarious marketing term for “100 Pre-written Sound Files”–making this what’s known as a “Wavetable Synthesizer”. Wavetable synthesis is a very easy and cheap way to create sounds because you can simply copy a bunch of sounds to the memory of the chip and then read through them sample-by-sample, changing the sampling rate to change the pitch (or having separate samples for each pitch value, depending how much memory you have to play with).

Further research reveals that we’re not the first to circuit-bend this particular keyboard. This example and also this one show some interesting possibilities, and by the end of this article we’ll have a better idea of what they’ve done. But enough talk, let’s crack this baby open!

Here we see the PSS-14 in its original state: operational, but missing the case screws (it was held together by duct tape when we found it). Perhaps a previous owner did some exploration of their own?

The preprogrammed songs cover all the major categories of music: Memories, Cool&Hot, Favourites, Fun Time. When we were younger we used to listen to Cool&Hot music all the time, but then it got mainstream so now we’re mostly into the underground Memories scene. You haven’t lived ’till you’ve heard the new remix of “Gallant Pig”.

There are twenty keyboard-controlled voices to choose from, most of which sound about the same. The volume controls seen here make a very loud “bongo” sound when you press them, no matter if the volume’s as low as possible.

Look Under the Hood

Clearly this thing could be better, so let’s open it up and see what we can improve about its operation.

The circuit board under the hood is pretty sparse, which is somewhat unsurprising seeing as it’s a wavetable synth and therefore most of the fun stuff is taken care of inside the microcontroller seen on the right. If you can find old electronic musical toys from before the digital era, you have access to a lot more of the nitty-gritty sound generation. Unfortunately those are much harder to find on the side of the road.

On the left side of the circuit board we can see the clearly-marked Vcc and GND connections, which would be easy enough to find from the battery terminals. The keyboard takes 4 AA batteries, which means it runs on a 6-Volt supply. We didn’t have the AC adapter for this keyboard so we’ll run it off of our bench-top power supply for now.
This hardly needs to be said but BE REALLY CAREFUL if you are going to use an AC-powered device. The bench-top supply we’re using has a current-limiter but a wall-wart transformer can push dangerous  crowds of electrons through your body, which we understand to be an uncomfortable experience.

On the right, we can see a bunch more resistors and–the holy grail–a clock component (it’s the blue blob to the left of the IC)! On digital synthesizers this is generally the main source of fun.

In the middle of the board there is a cluster of capacitors and what looks like a multi-transistor package. When we turn the board around and start probing, we’ll figure out what this is all about.

The soldered and printed side of the circuit board is much more interesting to look at. The dark patches that you see are conductive ink–this is a really common and cheap sensor technology used in everything from the humble NES controller to high-end Roland electric pianos. It’s a form of what’s known as a force-sensing resistor (FSR) and it suffers from major nonlinearity, hysteresis and repeatability. On the other hand, it’s dead easy to implement and it can be printed onto a board.

On the underside of the CPU we can start to characterize the pin functions. A lot of the pins go out to the various keys and buttons. A lot of those transistors that we saw topside are dedicated to this key matrix, too.

Scope it Out

Upon further investigation the button/key states are time-division multiplexed onto pulse wave signals based on a global excitation, illustrated here. According to this fellow who lists a circuit-bent PSS-15 (same model as this but with a silver control panel), connecting part of the audio output to the keyboard matrix returns can re-trigger buttons or keys to make “loops”. Very interesting, seeing as:

The keyboard uses a PWM-based DAC scoped here in comparison to the audio output further down the line. Again this is a very cheap technology (you can make one for your arduino pretty easily) and you can get a simple explanation here. Right off the bat we can see that a disadvantage to this technology is that its transition times between various voltage levels might be difficult to control, possibly leading to distortion. That aside, it will be interesting to connect the PWM DAC output to one or more of the keyboard matrix returns.

Here is a closeup of two interesting “hack points” on this keyboard. We’ll change the resistors on the right to see what it does to the signal, and we’ll change up the existing 8MHz clock for a different one.

The sine wave oscillations of component CL1 can be scoped to show a transformation into square wave, which we can safely assume is driving the operations of the microcontroller.

Modifying the Circuit

It just so happened that we had a spare 3MHz oscillator sitting around, so let’s find out what happens when we drive this device at 3/8ths of its normal speed.

A quick and dirty soldering job gives immediate results. In the video you can hear the results with the new clock and changing the resistor value at the PWM output–overdrive city!

Furthermore, by patching the audio output to parts of the keyboard matrix, we can create the “loops” as discussed eariler.
The results thus far have been, well, a little underwhelming. We can make the sounds slower and we can make little loops, and we’ve learned a little bit about consumer-level electronic toys. Still, at this point we were hoping to have unlocked some seriously badass digital fury.
Serendipity came to our help at this point, and an inadvertent touch of the oscillator legs produced the righteous vibes we’d been banking on!

The sounds that came out of this thing were incredible. Somehow, after assembly, this type of thing was happening at startup and it’s now only about a one in ten chance that the keyboard boots properly. Even then it’s at running 3/8ths speed… except some of the time, somehow, it properly adapts the PWM output so that despite the underclocked CPU the wavetables read at the original sampling rate. Who knows what is going on that ASIC.

What to do with it now?

At this point in our circuit-bending adventure we’ve characterized the operation of the device and found a couple of fun bends. Where to go from here? Well, one option would be to make the modifications permanent with the addition of pots, buttons, patchbays and what-have-you so that the end result is a sleek and performable instrument. We’ll be saving for a later date. Since, as we mentioned at the beginning of the article, it is quite possible to destroy a hacked piece of electronics simply by virtue of the stress caused by the modifications themselves, we’re going to finish this bend by recording the myriad new sounds that the keyboard produces, and composing a short celebratory piece of music:

Summary

While you may not have this exact toy keyboard at your disposal, the same techniques and methodology used here can be applied to many other audio devices. It’s simply a matter of

1. Taking your time
2. Understanding the technology
3. Characterizing the circuit
4. Experimenting

At the end of the day it’s not really that difficult to get started at this sort of thing–hopefully the concept of circuit bending has been demystified for some of you. This isn’t to say that circuit bending can’t go deeper than shown here, as this only shows the most elementary steps. And the complexity of the device you’re working with greatly affects the types of bends you can do–for example, the TR909 has many timing circuits that can be played with in much the same way as our Yamaha. We’ve recommended it and we’ll recommend it again, but for further reading be sure to check out Nick Collins’ Handmade Electronic Instruments. It contains a good section on toy hacking, and it’s generally a very good read.

If you enjoyed this introduction and want us to write further articles exploring different parts of circuit bending (or audio hacking in general), please let us know in the comments.

This thrift shop organ gets a new life as an 8-bit music maker. Called the Chipophone, it relies on an ATmega88 to produce sounds that you might associate with classic video gaming. [Linus Akesson] takes us through all of the different sound settings in the video after the break, including performances of your theme music favorites.

The original organ uses transistor logic making it rather easy to patch into the hardware. Thanks to the build log we know that [Linus] used 74HC165 input latches to monitor each of the switches for the 120 inputs. Fifteen of these latches work like a backwards shift register 74HC595, cascading all of the parallel inputs into one serial signal. From there the microcontroller takes over, monitoring the keys, pedals, switches, and potentiometers and outputting the appropriate sounds.

[Thanks 7e]

We’ve always put stock in ‘the quieter the better’ when it comes to road bikes. You’ll find this truth if you spend 100k on the back wheel of someone with a sqeaky rear derailleur. But apparently the folks at Effalo never learned this lesson as they’ve produced a bike computer that generates noise as you ride.

Perhaps it just takes some ingenuity to turn this into a beautiful music maker along the lines of the Force Trainer hack. No problem because the velosynth is a hackable design. The case was made with a vacuum form and inside you’ll find a bunch of small breadboards. The JeeNode, which is an Arduino/Xbee combination, serves as the heart of the device by taking speed and acceleration data from the bicycle wheel. From there it is passed on to various modules, Bob’s your uncle, and sound comes out. Check out their sales pitch after the break and if you’re starting to get some ideas about using this check out the open source info they’ve provided.

[Thanks Kristian]

This is an interesting take on a music box. [Blair Neal] is using an overhead projector with a roll of transparency to make a synthesized music box. A camera watches the projected image and feeds data to Max/MSP to produce the sounds. Customization merely requires creative image analysis. In this case, different colored pens or different tracks can be assigned to a sound with the speed of the track based on how fast you wind the transparency spool.

[Matt Kemp] remade this super 8 film camera into a synthesizer. Inside you’ll find a light sensor pointed through the lens. This way, zooming, focusing, and pointing the lens elsewhere will change the sound. He also refit the original controls to monkey with the output. Turn your speakers up when you watch this, your co-workers will love you for it.