I’m won’t go into how to set up a circuit bending workspace with all the tools you need (soldering iron, electronic components, etc.). There are plenty of resources out there to get you started in setting up a workshop. I am instead going to explain my exploratory process and strategy. A test lead with alligator clips and a couple of jeweler’s screwdrivers are all you need to get started. If you want to continue on to building a circuit bent instrument, then you’ll want to start creating a workshop with tools and components. You do NOT need to know a thing about electronics to start circuit bending.

So, you’ve gone to the thrift store and bought a toy or keyboard you’d like to circuit bend. The first rule is that it runs on batteries and does not plug into mains power. You want to live to bend again! The second rule is don’t circuit bend something that is of great value other than as a target for circuit bending. It’s one thing to experience the heartbreak of frying something that you were really looking forward to circuit bending but don’t care too much about unbent; it’s another to kill something you treasure as is it is, trying to make it better by circuit bending it. Valuable, rare vintage synth? Don’t do it man….

My first step after opening the device and exposing the circuit board is to touch it with fingers from each hand. Moistening the fingertips makes the circuit even more sensitive. Sometimes you will find sounds like feedback and noise just by touching. If you want to find pitch control, the device will have to be making sound. You will not be able to change the pitch if it is set by a crystal or resonator. Using this touching method works on devices which use a resistor to set the pitch.

I usually take a photo of a device’s circuit, add numbers to points on the circuit, and print it out as a reference. Below is a photo of the circuit board of a Buddha Chant box, and the same photo with points on the circuit given arbitrary numbers:

Next, with the test leads, I will try connecting all possible pairs of points. In this case, there are 9 points. I’ll connect point 1 to point 2, 1 to 3, 1 to 4, 1 to 5, 1 to 6, 1 to 7, 1 to 8 and 1 to 9, then 2 to 3, 2 to 4 etc. until all possible combinations have been tested. If I find something interesting, I write it down. For example: “3-7, pitch up” or “2-5 distortion”. It helps to write something descriptive, especially on more complex devices that produce a wide variety of effects when circuit bent. I like to categorize these discoveries in my notes: Glitch, loop, freeze, pitch up, pitch down, distortion, feedback, etc.

On more complex circuits, when I assign a number to a point, I like to draw a line along the circuit trace and draw an ‘x’ where the trace ends. All other points on the line between the number and the ‘x’ are connected to that number, so there is no need to waste time testing those points. Below is an example of this, The photo on top is unnumbered, the one below has numbers added, the traces are followed, and the point at the end of the trace is x’ed out:

A note about the circuit above (Radio Shack Electronic Drums) which can also be relevant to other circuits – often, directly shorting 2 points with a test lead may produce no results, but touching with the fingers may produce amazing results, because the human body has some resistance. For that reason, I like to start, as I mentioned earlier, by touching the circuit board. On the circuit above, instead of using a test lead, I held a jeweler’s screwdriver in each hand and tested all the many possible pairs of points. The sounds created actually change if you tighten or loosen your grip on the screwdrivers, and the device does not need to be making its own sounds to hear results this way. It feeds back, distorts, squeals, makes white noise. If I hadn’t tried touching the circuit first, I wouldn’t know its sonic capabilities, because most of these effects don’t happen when directly connected with wire. Effects that are obtained tactilely are implemented with “body contacts”. One method of adding body contacts to a device is to solder a length of wire to each of 2 points that respond to touch. You can then push 2 brass thumbtacks through the plastic shell of the device and connect one of the wires to each. These can be very expressive because the effects tend to change with the amount of pressure applied.

Continuing with the exploratory process, below are a numbered photo of the circuit board (top side) of a Coleco Talking Teacher and a page from the notes I made connecting the points during the exploratory process.

To take your explorations to the next level, you may want to consider buying a resistance substitution box and a capacitance substitution box. (You don’t have to get these – but they’re inexpensive). If you find a pair of points that produce an interesting effect, try connecting those points with one box and see what happens, then try the other. For example, if you connect a pair of points directly and it produces noise, you may find that as you add more resistance testing those points with the resistance substitution box, the effect will lessen. In a case like that, if you connect a potentiometer (or “pot” for short, which is a continuously variable resistor), you can smoothly control the amount of noise from none to full.

You can try the same thing with the capacitance substitution box. This may not often produce interesting results, but when it does, it’s impressive, especially with some Casio keyboards. If you find different capacitance values produce interesting results, you can add these to your circuit with a rotary switch that has a capacitor of each value at each point on the switch. I highly recommend having both of these boxes in your workshop – they are useful in many ways other than what I’ve described. Let’s say you find a pair of points on the circuit that causes the pitch to raise when you touch them with your fingers, but if you connect them directly, it causes the device to crash. You will likely want to add a pot to continuously raise the pitch (and lower it if you connect the other side of the pot the a point that lowers the pitch). Select the largest resistance value on the resistance substitution box and connect those 2 points through the box. Lower the resistance value until you find the highest pitch that doesn’t crash the device. Make a note of the resistance value you’ve selected. Now, when you add a pot, you can add a resistor of that value so that when you turn the pot to the highest pitch, it won’t crash. The resistor you add is called a limiting resistor. You can use resistors to set the low and high pitch limits. It’s much faster than using 2 test leads and manually connecting and disconnecting resistors or capacitors of different values, and is very helpful you don’t have a multimeter to measure resistance and capacitance.

In my first paragraph above, I stated that you do not need knowledge of electronics to get started in circuit bending. However, circuit bending can be a great gateway into learning about electronics. I knew next to nothing on the subject when I began circuit bending, but exploring circuits over the years has changed that quite a bit, and I do a certain amount of circuit design myself. Additionally, my pursuit of circuit bending sparked an interest in putting microcontrollers in my instruments to add even more functionality, so I purchased an Arduino and learned to write code for it. For, me circuit bending has been a source of continual learning and growth since I began in 2004.

My final contribution here is a link to my entry video for the Moog Circuit Bending challenge in 2011, for which I was a finalist. I demonstrate how I circuit bent a toy keyboard from start to finish. I am a dork, as you will discover: