bending bending bending and bending

A Tale of Two Bendings
As told by Eric Cook/Simulated.net

My first attempts at circuit bending.
After months of casting envious eyes towards Dave Wright's and Reed Ghazala's pages about circuit bending, I finally made the plunge and got down and dirty with a garage sale Casio SK1.

With the able assistance (and much steadier soldering hand) of my good friend John D'Agostini, we added a 4-way knob switch (4 groups of connections, each group with 3 wires and a control wire - I'm sure there's an official name for it that I've forgotten), and 3 bypass switches for the 3 control wires. All the wires go to various leads on the 3 ICs on the right hand side of the bottom of the circuit board. Each cross circuit has it's own sonic character, but by adding this many (and wiring them so that multiple short circuits occur simultaneously), we creating a distinctly non-linear feedback system. The results are chaotic, somewhat non-predictable and less than controllable. Since the feedback system is interacting with itself, the sound produced by the modded SK1 is dependant on starting variables (initial settings of the switches upon powerup), as well as previous interactions by the player with the system. As such, it's also very nonreversable - flipping from switch to switch does not always A/B/A/B the sound, but instead is more like A/B/C/B/AAA/C/Q/B/Q/X.

Lo-rez webcam closeup of new controls.

It crashes a lot, and also has a lot of "locked states" (the keyboard continues to make a sound or series of sounds but keyboard controls do nothing). There's also a certain amount of dud settings - where you simply cause the sound to stop, and keyboard controls do nothing. And frankly, it often sounds like a 4th rate electro-noise band, and given my lack of preplanning in the drilling, looks kind of hack-ass (especially compared to some of Ghazala and Wright's contraptions). That said, I'm very happy to have done it - and you've got to start somewhere, right? Even when the results are less than stellar, the feelings of exploring and modifying a sound-generating system like this are extremely satisfying. In some ways, it reminded me of the feeling after a good improv session, where you come out surprised at the results, not aware that you had to potential to create the music or sounds that you just summoned out of the air.

Audio Examples:
I can't see stopping after just one try on this, especially after getting over that initial reluctance to "pop the hood" and start looking around underneath. Future projects will be more sonically pleasing (or at least, that's the goal), but for the time being, here's two real audio files that demonstrate our results on this first project:

SK1 Feb. 19 Noodle Stream: demonstrates the wide variety (and unpredictability) of sonic results that were created, including distortions, waveform changes, ADSR alterations. I'm playing a couple one finger "melodies", but primarily just working the switches and nob that we installed. I'm not changing any of the pre-existing controls on the SK1 in this example.
SK1 Feb. 19 Beat Stream: the mods affect not only the sonic characteristics of the voices, but also the preprogrammed rhythms and melodies in the chord mode and demo song. Here, I'm playing in chord mode. I only actually touch the keys 2 or 3 times during this whole mess, to try and "kick-start" a change when the keyboard gets into a stuck-mode. Otherwise, all other alterations, melodies, etc come from playing with the mod switches.

Both files are 40kbps stereo real audio - not very fidelitous, but adequate for the examples here. And, no, neither of them sounds very good. :)

The Obligatory Incantor
So after a second SK1 mod (John needed his fixed up as well), and several abortive attempts at miscellaneous small and apparently too-simple-to-be-bent kids toys, I ran across a Speak and Math at the Salvation Army. We had put it off long enough, and decided to make an Incantor, the obligatory bend that everyone seems to tackle sooner or later. I was admittedly a little less excited about this one, simply because it did feel obligatory, rather than exploratory. Nonetheless, I was happy we did it, and fairly pleased with the results once complete.

Front of the modified Speak and Math

What'd we do to it? Two knobs and two switches were added: the top knob is a potentiometer that controls the "looping" (stepping through the voice/glitching array?); the bottom knob is a pot that controls pitchbend (many people put body contacts in for this purpose); the left button switch is a bypass control for the pitchbend, and the right is a "glitch" button. The glitch and looping have only partially controllable results when used in conjunction, probably due to my slippery soldering skills.

Closeup on the controls

No board scans here - we used Ghazala's Incantor schematic to find the points. Once you figure out what you're looking at, they're very clear and easy to use.

Here's a brief bit of demonstration audio:

Speak and Math Aug. 5 Demo Stream: 420 KB real audio file, dry recording direct to DAT, just demonstrating the pitch and glitch variations added. There's too much dead sonic space in the results that it creates for it to be used as a performance instrument, at least without a bunch of reverb and/or delay. The noisefloor for the whole unit, which wasn't low in the first place, has also been unintentionally raised. Still, seems like a good source material generator - I can hear some good rhythm loops in this stream already.

Additional SK1 board scans
Some visitors to the site have asked for scans of the wiring on the SK1 (one particularly optimistic gentleman asked for "a copy of your schematic".. schematic? what?), so despite the really sloppy job that we did (and my distinct impression that they will be, in fact, no use to anyone else), here's some a scan of the wiring. Perhaps they'll help you find some starting points.

(click for large image in new window)

Mmm, sloppy. (And to pre-empt the question - "All your wires are black..doesn't that make it hard to keep track of what you're connecting where?" Why yes, yes it does.)

(click for large image in new window)

Less useful, but included for the sake of completeness is this image of the wiring on the main bends control knob (a 3-position knob, with each position selecting one control and 3 toggle wires).

   Related resources:
    •    The Casio SK-1: Escapist Sample Shuttle, article by Q.R. Ghazala from
        Experimental Musical Instruments.
    •    Carrion Sound Modified Keyboards, lots of modded SK1's featured.
    •    SK-1 Info Page.
    •    Ghazala's Incantor Diagrams (abstract, but they'll make sense once you realize that the blobs represent ICs)
    •    Benders list on Yahoo. Occasionally plagued by the personality wars that infect any mailing list, but a good source of info and links all the same.

My Humble Advices
by John D'Agostini/Noizehole.com

- it's all broke baby, don't worry about being "careful" or "proper".
- battery powered devices reduce your risk of accidental deadly electrical shock.
- bending alone ? the "demo" or "demonstration" song/button is your new best friend.
- bending together ? bender#1 works the keys/resets power, bender#2 is circuit side jumper monkey.
- be prepared for LOUD BEAUTIFUL RANDOM CRASH.
- some devices just don't want to bend period. sorry.

** thanks to Eric Cook for introducing me to the wonderful world of bending **