Pitchfork arpeggiator – v1

So this is an old project, but I only recently found some documentation i had of it. v2 is almost ready, and I’ll post an update soon.

This “pedal” is a controller for the EHX pitchfork pedal. It sends a Control voltage (via an arduino controlled digital potentiometer) to the pitchfork’s expression jack. This mimics an expression pedal, but lets a player pick out specific notes, instead of sweeping through a range.

The concept is fairly simple. You first “tune” the pedal by finding the digital pot values that correspond to specific notes. Once you’ve got those values, it’s all a matter of controlling the values you send via the arduino. You can do other fun things like make an arpeggiator out of it, or use it as an extra pedal synth tone while jamming.


On the “One”

Here’s some words of wisdom from Bootsy Collins, which highlights one of my biggest musical struggles:

Keeping things in time is necessary for music with repetitive phrases, or riffs – pretty much the foundation for most popular music. You can go by “feel” when you’re playing live with other musicians, but it’s a bit different when you play alone in your bedroom with a bunch of electronic gadgets – it isn’t easy to play together to create a recognizably musical composition. Its useful to have a way that instruments can communicate with each other so they can reliably respond to each other’s timing to anchor abstract jams, or trigger actions at appropriate intervals.

Fortunately, there is a language they can use to communicate – MIDI (this doesn’t necessarily simplify things, since instruments speak a variety of different dialects). But not all my instruments (eg; guitar) are MIDI enabled, and the only way I can layer them is by recording loops, and playing them back using triggers. My current studio/performance setup desperately lacks a reliable method of sampling audio loops in a way that follows Bootsy’s funk formula – i.e, start together on the”one”. This could be solved by having a master clock source (the volca beats drum machine) trigger recorded audio at the start of every drum sequence, or multiples of the same. There are a few tools that can help you do these with hardware gear, from Ableton to fancy loopers with MIDI capability – but I would have to empty my wallet to obtain them, and where’s the fun in that?

A few months ago I built the Where’s the Party At? sampler – which is amazingly featured for an inexpensive, lo-fi DIY project. It has a pretty thorough MIDI implementation and I was able to get loop syncing going pretty easily via an axoloti patch. It triggers the default recorded note every few bars, and I can control the parameters by which they synchronize – which allows me to new melodies and patterns.

There are less complicated methods of doing the same thing – but this makes it fun, and the axoloti is still free to run other things, like a live sampling patch (for some chaotic sample-ception). Here is a simple clip I recorded with this setup, using just my voice and the volca beats for sounds (voice -> axoloti [with a sampler patch] -> WTPA2 [MIDI in via the volca]).


A few years ago, I bought a kit of Jason Hotchkiss’s Le Strum midi controller project. It’s been lying around in various stage of incompleteness since then, as I’ve been trying to figure out what to do with it.

Here is the first usable prototype – I tried to make the enclosure a cross between a guitar, an accordion and a kalimba. This is how the controller works:With your left hand, you select the chords you want to be mapped onto the spokes, while your right plucks the notes you want to play from those chords. The chord keys are mapped out in a circle of fifths, as in an accordion, while the notes get mapped onto the spokes in triads over a range of octaves. Combinations of keys allows you to choose chords with added voicings, like major/minor/dom 7ths, and add4/add6 chords.

As for the name – an Mbira is another name for the family of instruments the kalimba belongs to, so MIDIbira seemed appropriate.

Here’s a brief video:

Guitar/kalimba MIDI thing #lestrum

A post shared by Saurabh Levin (@saurabhlevin) on

Fun thing I discovered while 3d printing the enclosure – if I angled the parts at 45*, no extra support layers were printed, which greatly reduced my print times.

Potential updates:

  • A wooden enclosure instead of a 3d printed mess
  • Laser engraving faceplate with labels
  • Redoing the entire thing as a MIDI foot controller (eek – but this could be really useful, as a guitarist who likes to have my hands free)

Banana Apparatus Mixer/Patchbay

Here is a fun utility box I made sometime last year that that’s been seeing quite a bit of use. It’s a patchbay with two channels of mixer and splitter circuits, which allows me to mix and play with signals in a hands on, and (relatively) hassle free manner.

This slideshow requires JavaScript.

It consists of 6 X 1/4″ -> 1/8″ jack convertors, which allows for easy patching for multiple effects pedal loops (3, usually) using the mix of patch cables. Different signal loops can be blended and split using the mixer modules on top. The blending can even be controlled via an expression pedal, which allows for some interesting effects.

This Document contains the schematic I used for the mixer/splitter: Splitter Build Doc

The mod to control the blending via a footpedal isn’t too complicated. When the expression pedal jack is inserted at the top, a switching jack disconnects the blend knob and rewires the leads to the expression jack instead. This image helps visualize it.

Katari Punk Console

This here’s the Katari, or the kit version of the Atari Punk console that I helped put together while at ISRO. It’s based on the Atari Punk Console and aimed at being used for workshops for electronics and noise making. (http://www.jameco.com/Jameco/PressRoom/punk.html?CID=punk). It’s more or less the same design, just housed in little electrical boxes you can find for 20rs or so. We added 2 light detecting resistors to make it a little more interactive and fun, as well as switches to select between the different controls. It’s a gloriously noisy little thing.

This slideshow requires JavaScript.

kit version

Modded Voice Looping toy

A friend got this fun voice looping toy from the souvenir shop at MoMA that lets you record 3 second long clips and play them back. It has a pitch/speed shifting dial, which is fun, but it does lack one or two features that could make it pretty usable. To remedy that, I added an option for line out, and a toggle switch instead of the pushbutton, so that it could play back a given loop infinitely. Here’s a quick test of the same:

Gear: Hacked MoMA voice box-> MXR Blue Box-> Digitech hardwire looper

Career Fair workshop

Last week, Arun and I did a workshop at a career fair for ITI graduates, which took place at Freedom Park (Bangalore). It was organized by Quest Alliance, an NGO that works with Design in Education mainly with students from ITI’s (Industrial Training Institutes). ITI’s are government-run colleges that provide students with the basic skills to do the job of, say, an operator or craftsman.

As with any other engineering institutes, ITI’s (or any institute, for that matter) are plagued by the usual issues of teaching being imparted soullessly, as a means to a lievelihood, and without any idea of individuality of the student. After initial ideas flitting around doing an arduino workshop with them where they’d learn the necessary skills of using the arduino environment and basic prototyping techniques, we decided we weren’t quite experts in the field ourselves, and tried a new track.

We decided to focus on introducing them to open-source projects and doing innovative and fun things with low-cost alternatives. It seemed more valuable to show them the available possibilities of DIY tech, for us as well as them….seeing that this was our first time taking a workshop like this, it didn’t make sense to go in acting like we knew what was going to come out of it. Anyway, here’s a summary of what happened:

We began with a simple demonstration of the DIY webcam microscope, as a sort of icebreaker. It got their attention, but the number of times I practised that routine beforehand made the sensor get all foggy, which did dampen its impact somewhat. After seeing a couple of fuzzy pixels on my laptop screen, we progressed to showing them some stuff we’ve worked on as Ternup, from our low-cost water testing kit (Caddisfly), and the simple colour sensor hack we based it on, to our DIY rain gauge using piezo discs as contact microphones, just to give an idea of some basic technology that could make a difference if just used a little differently. They seemed pretty intrigued by the contact mics, as they associated the parts with the buzzers that are usually found in toys and greeting cards .

This slideshow requires JavaScript.

Since we had finally segued into the topic of making a potential racket, it was time to get down to making synths.

We had a bunch of students who had no idea about electronics, so we skipped most of the techy bits of the presentation, and had them try to make the arduino synth – the Auduino. The circuitry required to set it up is extremely basic, just a few pots and wires (the fun stuff happens in the code) so they managed to connect it up fairly quickly and listen to their instruments as well (they seemed to be in a  hurry to be elsewhere).


We gave the to-be-engineers (who had done soldering, and were used to working with breadboards and building basic circuits) an analogue synth called the Atari Punk Console. It’s pretty easy to make, although not simple enough for the two hour long session we had. I forgot that, as with any other circuit, it required approximately the same amount of time to troubleshoot it as to make it.

Atari Punk Console

They did get a few wheezy squeaks out of the badly grounded circuit, though. At the end of it a couple of them came up and asked me to give them the circuit diagrams so they could try making it at home.

Anyhow, they left mostly without the expression that we had irreplacably stolen 2 hours of their life, so I guess that went well. For a first workshop along these lines for either of us, perhaps more so.