Creative, curious minds have always
modified and enhanced audio hardware.
But in the past two decades, a growing
number of people have hacked into circuits
to transform simple instruments into alien
beasts of sound.
THE TERM “circuit bending” was coined in 1992 when Reed Ghazala began
publishing a series of articles in the Experimental Musical Instruments Quarterly
Journal titled “Circuit Bending and Living Instruments.” Ghazala, who had
developed his skills since the late ’60s, defined a couple of simple rules that would
enable anyone to safely explore and modify audio electronics, without a degree
About ten years later, the first annual meeting of circuit benders, the Bent
Fest, was organized by Mike Rosenthal and Daniel Greenfeld at The Tank. For
three days in the spring of 2004, this lively mid-Manhattan art space brimmed
with energy from the many creative forces that came from all around the world
to attend the gathering. The festival included workshops, tutorials, concerts, and
showcases centered on the creative use of electronics that were not necessarily
designed for the purpose of making music. This event, which lasted until 2011,
became the annual meeting of the creative crop of circuit benders and hardware
hackers, and was the birthplace of some highly individual electronics and sounds.
What is Circuit Bending? So, what is
it, really? How do circuits bend? The short
answer: Circuit bending describes the
modification of an electronic sound device
beyond the designer’s intentions, adding
new sonic and functional possibilities.
Although there are many approaches to
circuit bending, in general, the bending target
will preserve its normal operation and is just
enhanced with switches, potentiometers, body
contacts, or jacks that will invoke the functions
Circuit benders usually are not electronics
experts, nor do they have service and repair
manuals for the devices to be bent. The
process of bending is one of trial and error,
carefully avoiding risking the health of both the
bender and his target. Anyone, even children
(supervised by a seasoned bender) can do it, as
long as some basic rules are followed.
The Rules The first and most important
rule is written in stone: Never bend
anything that plugs into the wall. Circuit
bending is strictly battery powered. The
safety risk is just too great. The maximum
voltage considered safe at all times is around
6-9 volts. That range complies with most
common bending targets, which are powered
by 4 or 6 batteries. (I make one exception
with the Suzuki Omnichord, a wonderful
bending target, which needs to be powered
with 12 volts.)
Do not bend anything that you are dearly
attached to, or is difficult to replace. Usually
circuit bending does not harm your targets,
but sometimes things go wrong and you might
accidentally fry the piece you are working on.
It has happened to me, so be warned.
Avoid contacts that produce loud pops
and clicks, drop the volume substantially, dim
displays and LEDs, or heat up components
significantly. Also, avoid the area where the
power supply connects, especially these pins
Be aware of electrolytic capacitors. Elcos
that are bigger than a cigarette tip can store
a significant amount of energy that will melt
the tip of a screwdriver when shorted. Never
reverse polarity or they will explode. Wear
The Tools You will need some basic tools to
perform circuit bending:
|The Suzuki Omnichord OM-27 before and after bending. The three silver knobs on the lower side belong to a Ibanez DE-7 delay.
• A set of screwdrivers (especially
Phillips nos. 0, 1, and 2, and some flatblade
models) to take apart the device.
You’ll also need a set of watchmaker’s
screwdrivers for tiny screws and to access
individual points on a circuit board.
• A wire cutter, pliers, and a tweezer, to
handle screws, wires, and other parts.
• A couple of cables with alligator clips.
• A low-wattage soldering iron and some solder.
• A drill and a reamer, to make holes for the
additional parts, such as switches and pots.
• Assorted parts: resistors, cables, capacitors,
diodes, LEDs, body contacts, etc.
• Gaff er tape. This will help you to keep
internal batteries in place.
• Helpful but not mandatory: a multimeter to
measure voltages and resistance.
The Targets Okay, we know the rules, we’ve
got the tools. What can be bent? Pretty much
anything that is battery operated! I have seen
people bring some awkward things to bending
workshops, such as a broken wireless phone
from the dumpster that was transformed into a
funny dial-tone feedback-screamer. But usually,
small keyboards, speech-generators, stomp
boxes, drum machines, or cheap Chinese sound
toys are common bending targets.
As a rule of thumb, consider the 1980s as
the Golden Age of bending targets—especially
the small keyboards manufactured during
that time by Yamaha, Casio, and lesser-known
brands that had very limited “intelligence”
onboard. These instruments are easily
“convinced” to interpret their operational
information, hard-coded in ROM chips, in
unusual ways by shorting some pins with
other pins. This will lead to surprising and
often beautiful results, soundwise, but also
with the arpeggiator and play-along features
of the instruments. Most modern synths with
more sophisticated CPUs will crash when you
attempt to bend them.
The Yamaha PSS-270 and Casio MT-240, as
well as speech toys like the Texas Instruments
Speak & Spell family, are among the great
bending targets, with simple logic and big,
easily accessible ROM chips.
|The basic bending tool for shorting selected pins on a circuit board. With two alligator-clip cables, you can place components such as a pot or a capacitor between pins.
Some devices that off er very limited
“standard” capabilities can be greatly enhanced
with body contacts. The Suzuki Omnichord or
the rare KoolShades Electronic Drum Set, or
even a Boss Metal-Zone MT-2 distortion stomp
box, are great body-contact targets.
It is a good idea to search the internet for
information on the specific device that you
intend to bend. Apart from instructions and
how-tos (which in my opinion spoil the fun of
exploring the possibilities), you will often find
at least some feedback on the “bendability”
of your device. Occasionally, and this is an
exception to the rule, some instruments turn
out to be duds, where no bending attempt
shows any usable result.
Bending Techniques Bending targets are
highly individual in terms of modifications
that will work on them. There are three basic
modifications that you can apply individually
or combine on most of your bends:
Short two (or more) points on a circuit
board. Depending on the instrument and your
preferences, this is performed with a switch, a
momentary switch, or through a patch bay.
|Bending setup with bending box and external power supply from a 12-volt battery through an LM 317 power regulator. The target is a Casio SA-20.
Connect two points through a resistor of
a specific value, or a potentiometer (which
is an adjustable resistor). A special resistor
that changes its resistance as a function of the
brightness of light (LDR) is a nice mod that will
allow you to use gestures instead of touching
a knob to control your bend. For best results,
combine that with a pot to control the range of
effect. Often, resistors of any kind are combined
with a switch to turn the bend on and off .
Use a body contact to make you part of
the circuitry. By connecting one or more
points you will act as a variable resistor, like
a pot. The more surface you touch, the lower
the resistance will be. Some connections
will work only with a fairly high resistance.
The resistance of your skin falls between
100 kilohm and 1 megohm depending on its
moisture. If you have very dry hands, the
resistance will be in the megohm range; if you
have sweaty hands, it can be below 100 kilohm.
Other electronic parts, especially capacitors
but also diodes, coils, etc., might have the right
effect on your bending target. It is up to you to
try them out.
Preparations Before we start exploring our
target, we should prepare our setup. In most cases,
you can open the target by loosening the screws
on the back side of the instrument and carefully
taking off the back. The wires connecting the
battery compartment are often quite short and can
rip off easily, so take your time.
Now we should see some sort of circuit
board, mostly showing the soldering side.
Take a photo of the soldering side (and also
of the component side, if easily accessible),
and print out a couple of sheets. (I prefer
bright, black-and-white prints.) This will be
your “notepad” to mark the hot points on
the circuit board and take notes about their
behavior with other points.
|The Casio SK-1 is one of the best-documented and explored bending targets, with a wealth of great bends and a stable and reproducible behavior. This model is enhanced with a breakout box for the additional components.
It is always a good idea to write down
the labels of the chips and Google them. For
most chips, you will find data sheets that will
explain their function and show the pin-out.
That way, you will know the pins where the
power supply connects, and avoid them.
It is tempting to just solder up whatever
you have found, while exploring the circuitry.
But the photo method will reward you with
valuable info for later reference and encourage
you to plan the best layout and bending
technique before you start drilling holes.
Speaking of soldering: If you have never used
a soldering iron, it is not a good idea to start
soldering right on your bending target. Find
an abandoned circuit board (such as a PCI-slot
graphic card) to practice on; there are many great
soldering tutorials out there on the web; see the
“Helpful Links” sidebar for more information.
After you have successfully soldered some cables
to neighboring contacts on a chip, without
shorting them or just “glueing” the joint (by not
heating it up enough), you are ready to work on
your bending target.
Let’s Get Started! For this example, we will
bend one of the most rewarding and iconic
bending targets, the Casio SK-1 sampler. After
batteries are fixed in place, we will start our
exploration by checking the circuit board for
|Fig. 1. The circuit board of the Casio SK-1. Here, three double rows of pins mark the ROMs. Note two main-points on the ROMs, and some of the interesting connections. There are many more possible connections, but not every single pin needs to be checked; some of the pins already connect to others on the same or another ROM.
On the left side of the circuit board,
three vertical double-rows of pins indicate
the three ROM chips; this is where we start
(see Figure 1). Now we need
our alligator clips. Link two watchmaker
screwdrivers with it, and presto—there is
your “precision bent-point detector.”
Now we come to the somewhat
uncomfortable fact that we need make the
instrument play while we are working on the
back. Luckily, most synths have demo songs
that start on one button press, so we can
use those and concentrate on the backside.
Choose one of the pins as a master pin and
connect that to all other pins on the ROMs,
while the demo song is playing. You will notice
the sounds and playback patterns change
significantly, but the connection of some points
will crash the instrument; you will know this
has happened when the sound freezes or
mutes and nothing happens when you press
any buttons or keys. This is not a big issue or
reason to worry. Disconnect the battery or
switch the SK-1 off and back on and start over.
As this procedure is somewhat tiresome, I
install an NC (normally closed) momentary
switch into the positive battery wire (red), so
I can reset the SK-1 with the push of a button,
with easy access.
In addition to the ROMs, you’ll often find
some kind of tuning trimmer. You can connect
that with a variable resistor, like a pot or an
LDR, or a combination of both, to certain
points on the circuit board. Sometimes these
trimmers relate directly to the speed of the
CPU; to keep it from crashing, a minimal
resistance needs to be detected and inserted as
a resistor at the wiper (middle) lug of the pot.
Be sure to make this mod switchable, so you
can always fall back to the original tuning.
|The KoolShades drum toy is a very lively body-contact bend. Note the upholstery tags used for the body-contacts and the mark sheet.
Over time, you should have marked the
good and bad spots on the ROMs; now,
think about your preferred way of making
them accessible. There are many ways to
do so, especially with the Casio SK-1. (For
inspiration, search the Internet for pictures
of bent SK-1s.) The space inside is too
tight for everything to be wired up in the
instrument itself, especially if you don´t want
to sacrifice the speaker. So, if you like to max
out the possibilities, it might be a good idea
to use an external box and use a multicore
cable to connect your switch or patch-board
to the SK-1.
The procedures described here apply
for pretty much all keyboards with ROMs.
If the target is based on FM synthesis, such
as the Yamaha SHS-10 or PSS-270, cutting
the data lines between FM chip and CPU
and rewiring them to switches will bring
out the amazing sonic possibilities of FM
synthesis beyond the “normal” sounds found
in the instruments.
Body Contacts One of my favorite bending
techniques is the use of body contacts. Body
contacts provide very tactile and sensitive
control of a connection; unlike switches or
pots, they are as subtle as the fretboard of
a violin, altering tone and timbre with the
slightest movement. Almost every bending
target has at least some body-contact points
at the amplifier section. But usually these
produce only very loud feedback.
But some bending targets, especially
ones where the sounds (or lots of gain) are
produced by analog circuitry, offer a wide
range of feedback, at a controllable level.
Finding body contacts is really easy, and it’s
the first thing I check on any bending target. I
simply touch the circuit board with my fingers
(moistening them a bit if they are very dry). If
you have found areas that work nicely, it is time
to grab the watchmaker screwdrivers (this time
without an alligator-clip cable between them)
and break things down to individual points.
The best way to make those points
accessible on the outside of the instrument is
to use upholstery tags. These are cheap, easy
to install, and have a nice feeling to the touch.
Most importantly, you can solder wires directly
to them. Drill a hole slightly smaller than the
tag’s pin, push it through the plastic case, bend
it a little to keep it in place, attach the cable,
and you are done.
One of my favorite body-contact feedback
screamers does not even need that step. The
Boss Metal-Zone MT-2, a distortion stomp
box with high, low, and parametric EQ,
has so many interacting points that I just
sanded down the spiky pins on the board and
rehoused it in a lightweight plastic case.
Tool of the Pros: The Bending Box If you
like to practice circuit bending on a regular
basis, you may want to optimize the process
of exploring your target. A really helpful tool
that you can easily build yourself is a bending
box, which will contain assorted common
components like a switch, temporary switch,
body contacts, LDR, LED, capacitors, and
a resistance decade. A resistance decade
is made of pots connected in serial, with a
resistance that increases ten-fold with every
pot: 10 ohms, 100 ohms, 1 kilohm, 10 kilohms,
100 kilohms, and 1 Megohm would be the
values of choice. This tool will enable you to
precisely dial in any value between 1 ohm and
1 Megohm, which is very helpful to determine
the best resistance or pot-range value for your
special bend connection.
|Above right, bending box; below, its schematic. Note that the resistor cascade can be used
in series with all other components with the switches S1-S3.
The bending box I built for myself also
doubles as a power conditioner. I use a 12-volt
gel/lead-acid battery through a simple circuit
around a LM 317 power regulator, which lets
me dial in any voltage between 3 and 11 volts.
Gel-lead batteries are cheap, reliable, and will
easily work for a decade if you charge them
properly after every use and never deplete
I’ve only introduced you to the basics of
circuit bending. There is so much more to
learn and explore. Check out the books and
Links listed here for some inspiration—and
have a nice bend!
Joker Nies lives in Cologne, Germany. He is a
musician, recording engineer, circuit bender,
and editor for Sound & Recording and
Keyboards magazines. His circuit-bending
career started in 1995 with a Suzuki
Omnichord OM-27, which is still one of his
favorite instruments to play.
These are bending targets with proven
bending potential. This list is in no way
complete; you will find more models on
Casio SK-1, SK-5, SA-2, MT-240, SA-10,
MA-101, Concert Mate 380 (SA-2)
Yamaha PSS-270, PSS-470, PSS-780,
Texas Instruments Speak & Spell, Speak
& Math, Speak & Read, Touch & Tell
V-Tech First Talking Computer, My Little
Talking Computer, V-Tech Apple
Distortion/body contacts: Boss MT2
Metal-Zone, Boss DS-1, Pro Co Rat
Delays: Ibanez DE-7, DL-10
Korg DDD-1, DDD-5
Roland TR-505, TR-626
Yamaha DD-6, RX-11
A great guide to
start out with,
you are totally
is Reed Ghazala´s
Build Your Own
Alien Instruments. The master shares
his knowledge by explaining every
step, electronic component, and
technique carefully and in great detail,
for many bending targets.
read, with lots of
the world of
Music: The Art of
by Nicolas Collins.
It also starts with detailed basics and
unfolds into building your own little
sound circuits. It also features an
amazing collection of examples from
sound artists, in pictures, description
and sound (on DVD).
drawn book to help
you get familiar
Forrest Mims III’s
in Electronics. Its
appealing drawings make this book an
easy-to-understand read, covering all
aspects and components of electronics.
Reed Ghazalas’ informative homepage,
with lots of info and photos of his
gorgeous creations: anti-theory.com.
Issues of the
online on CDROM,
in case you want to read Reed
Ghazalas’ original articles on circuit
A great collection of information on
many common and rare toy keyboards
and bending targets: weltenschule.de/
Lots of info on all aspects of the topic:
This page specializes in stomp-box
The British branch of circuit-bending;
many drum machines found here: