Blog: entries tagged with "midi"

The Bee and the Express

Express: back panel test mount I’m finally back to working on some electronic projects. First up, the Express, an analog-to-MIDI converter built around a Bare Bones Board, an inexpensive Arduino clone.

I’ve been making up some patches for my Evolver synth to use it as an effect on guitar or bass, and thought it’d be nice to have some sort of pedal to control it, along the lines of a wah or volume pedal. The desktop model of the Evolver lacks a pedal input, hence the Express (for “expression”, both of the musical and genetic kind - evolution, geddit?). Currently, it reads one analog pin and spits out continuous controller data. Nothing particularly spectacular there, but it did fit wonderfully into the sturdy steel case from a computer keyboard A/B switchbox. There’s room for lots more inputs, and eventually I figure it’ll sport an additional analog in and some footswitch inputs which will send things like note on/off messages.

I’m still new to making enclosures, and to working metal in particular - instead of grinding out a hole that was slightly too narrow, I used a drill, which grabbed hold of the edges and warped the heck out of the front panel. Panic set in for a moment, but I managed to bash the thing back into shape using a busted old hard drive(!) as an anvil.

Word to the wise: there are two incompatible standards for the wiring of expression pedals:

1/4” - tip to wiper / ring to +5V / sleeve to ground: Clavia, CME, Electrix, Emu, Kurzweil, Oberheim, Roland/Boss
1/4” - ring to wiper / tip to +5V / sleeve to ground: Kawai, Korg, Yamaha

The former arrangement allows you to use a standard normalling jack to connect the tip to ground by default, so the input doesn’t float if nothing’s plugged in. I’m using a Boss pedal now, but my other pedal is a Yamaha, so if I want to use it as a second input, I’ll have to wire up something to cross those connections.

Arduino (and Tarquin) Being easily distractible by possibilities - giant trackball! LED matrix! stepper motor-controlled time-lapse photography! - I’m desperately trying to focus on a couple of projects at a time. Arduino project number two at present is using it for ultra-cheap and dirty sound generation, with piezo disc speakers plugged directly into the digital outputs. A little hacked-together code, and voilà:

The Bee (MP3, 640k)

I call it the Bee, though “Mosquito” might have been more appropriate. Modulating the pulse width creates some nice motion, but there’s a lot more to do, like getting R/C filters to tame some of the harshness - it really is annoying after a while. Oh yes, and putting a switch on it to shut it up between tests. And, of course, buttons and knobs to play it with… maybe even some sort of acoustic treatment, like a resonating soundbox or a spring reverb.

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Musical interfaces 2

the displayBehold the two-digit display for the Box-O-Knobs (also seen here with its breadboarded ancestor). Each digit is run by one 74HC595 IC. Resistors everywhere. The reverse of the board is a bit hideous, I’m afraid, thanks to my still-amateurish soldering skills.

The vacated breadboard now sports five knobs (50k rotary pots), a MIDI socket and a photocell, which I’ve got controlling the sixth analog pin on the Arduino. A change on any input sends a MIDI controller message. The Evolver already has provision for reading in mod wheel, channel pressure (aftertouch), breath controller and foot pedal information, so I’ve got those wired in along with pitch bend and volume.

Next steps:

  • figure out how to cut the appropriate slots in the top of a case
  • wire up six slide pots as controls
  • external input jacks that override the faders
  • buttons!
  • calibration and MIDI settings editable by the user, without having to recompile and upload new firmware.

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Musical interfaces

We have MIDI!After a good deal of poking and prodding, I got my Arduino board to speak MIDI! The current program reads a potentiometer and sends pitch bend messages down the pipe.

Had a bit of worry when it just sat there doing nothing, but it turned out that I just had the signal and +5V leads reversed. Bonus: if your computer isn’t talking to it via USB, it’s just fine with being plugged into USB and MIDI at the same time. Makes for much, much easier programming.

Invaluable resources in this effort: circuits and code from Tom Igoe, of the Interactive Telecommunications Program at NYU, and Sebastian Tomczak’s blog little-scale, which includes news of his Arduino / MIDI projects.

The more I think over that guitar string ribbon controller idea, the less it strikes me as a permanent solution. I like that it’s quick and cheap, but it’s going to rub the oxide off the tape (or whatever I use as a resistance). So the design will have to take replacement of the tape into consideration. The guitar string method may be useful for building multiple controls - I’d love to have something you could play like the fingerboard of a bass. No rush there, though.

A capacitive position sensor would be a better alternative - that’s what computer touchpads / trackpads use, and among other advantages, they can be placed inside a case so you never have to touch the actual sensor element. Durable is good, especially where musical instruments are concerned. And they generally feature serial output, which I can feed to the Arduino.

Cirque make some promising-looking devices, including some standalone models. Of course, most of the ones I’m interested in are OEM and hard to come by for someone who’s not designing laptops for a manufacturer.

But why buy new when they’re going for scrap all over? A quick search on eBay turns up masses of laptop frames - just the panel that goes around the keyboard, and including the touchpad. I’ll have to hit some local surplus and computer stores too.

Code and sounds to come.

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Just like homemade

Neat project: Freqtric, a system that senses body contact and uses it to trigger MIDI drums (and presumably other instruments).

I don’t know if this is part of the device, or future plans for it, but I’d love to see a version that senses which two people have made contact - imagine a dance piece choreographed around a system like that! Ideally it’d be wireless, but that would kind of defeat the skin-resistance effect the Freqtric project uses. Maybe something using conductive gloves…

IMAGETaste of the Danforth was this weekend. Utter madness. One mile of Danforth closed while hundreds of thousands of people mill about lining up for cheap food and free samples. We caught a few minutes of music from a Cuban band, which caught my ear because I’ve been working on a new arrangement for “Catch-22”, our ostensibly Latin number. Sat up into the wee hours last night hammering out a bassline for it. It’s gonna groove.

Also, this week has been awesome for jamming. Found a very cool bunch of folks who are into free-form living room music-making. Very excited!

Also, my latest score from Active: DPDT switches, for the making of stomp boxes.

Also, I salvaged the caster “tree” from a dead swivel chair and a busted coat rack from the office, for the making of percussion stands.

I’ve rediscovered my true packrat nature. I’d been denying it for some years - partly I was paring things down, partly I was influenced by my SO’s firm belief in chucking things that don’t get used, partly it was because we move house every year or two. But now my packratting has purpose. I actually am building things with the junk I collect. Castoff things are an opportunity.

Building things from materials at hand - it’s a trait I inherited from my parents, and I think the whole attitude is one of their greatest gifts to me. Almost every piece of furniture we had was either a hand-me-down, bought used, or home-made. We just didn’t buy new things unless we really needed them.

  • For much of my childhood, our couch in the living room consisted of sleeping bags laid on top of foam on a bed of old wooden microscope boxes (which were all filled with old books, or tools, or five-pound chunks of rock with embedded fossils).
  • We had a little tractor/riding mower - that was bought new. But my dad built the trailer for it by sticking a box made of pegboard on top of an old lawn mower frame.
  • Mum sewed stuffed toys, including a whole basket of vegetables and a completely awesome dragon. Most of my toys were homemade too.

Of course, this filtered through to me - I’ve mentioned the surplus walkman before. On the music-making front, I made use of: kitchen utensils; cassette tape loops; weird instruments my parents had collected, like a psaltery, a manjolin, an ocarina; an early PC speech synthesizer fed through a disembowelled toy spring reverb; sound effects records spun slow, fast, and backwards; an electric guitar with its signal crammed through a Commodore monitor and my mum’s walkman speakers (I toasted them, along with many other devices); and a practice chanter for learning the bagpipes. These all showed up in the recordings of the Spastic Attack Dogs (a grand high school band name if ever there was one) - who reunited after university, learned to actually play, and became Flickershow.

After I moved out, I snagged an old wooden door from Mum and Dad’s place, propped it up on a pair of cabinets, and used it as a desk. It worked well except for the layers of peeling paint on it, which got worse due to me spilling water on it and frequently using it for drum practice. When my BF and I moved into our first apartment together in Toronto, I decided it was time to strip the paint off it. It turned out there was a layer of milk paint on it that wouldn’t budge, so we gave up, sanded the bugger to a splotchy, hideous, but smooth finish, and got new legs for it at Ikea. I still get ribbed about the “Eli and his *&#$ door” incident, but it’s big enough for two monitors, a synthesizer keyboard, a printer and a mixer, and I never see the surface of it anyway.

So of course I was delighted to discover ReadyMade, which is a magazine aimed square at people like me. Looks very cool - I even tried to subscribe, but their online subscription system broke in several ways and I got fed up. Will have to let them know.

So here’s my ongoing list of electronics projects, in rough order of difficulty:

  • An expression pedal (based around a fader rather than a rotary pot) - the electronics are bonehead simple; it’s the woodworking to make the rocker that’s the tricky bit. Starting with locating our hand saw.
  • A box with a simple photocell circuit for use an an expression-pedal input. Controlling something like the FilterQueen will require a more complex thing with a transistor or two, but I ain’t ready for that yet.
  • A ribbon controller. (All praise the late John Simonton.)
  • A simple fuzzbox circuit or two, snagged off the web (there’s loads of DIY stompbox circuits out there).
  • And way down the road: a “fretless” electronic instrument that feeds a signal from a piezo pickup through an analog-delay comb filter with the feedback turned way up, creating a ringing tone. The delay rate, and thus the pitch, is determined by a ribbon controller. I’m picturing two or three of these stacked together to resemble a very nerdy guitar. Left hand fingers notes on the ribbon-controller strings; right hand thumps and taps and scrapes a set of pads in which the piezo pickups are embedded. There’s another control for damping/feedback, but I don’t know how that’s handled yet. Lots of learning to go before I tackle that… but it’s one I’ve had in mind for a long while.

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Bookmarked in case I ever get a little MIDI controller here: midiStroke, which will convert MIDI messages to keypresses in OS X. With a bit of work, it could be used to add some real, physical controls to Photoshop: twiddle a knob to adjust the flow on the Airbrush tool, that sort of thing. Pity there aren’t keystrokes for adjusting the current paint colour…

IMAGEAlso, I happened to stumble on a listing for a synth called the Dave Smith Instruments Evolver. Just reading about it makes me want to weep with joy. It really does sound like my dream synth: all sorts of modulation possibilities, external input (which can trigger or modulate in different ways), all sorts of feedback paths… And the editing software they offer lives up to the name ‘Evolver’ too, with genetic patch generation - you can generate new sounds a little like you were breeding plants.

All of which adds up to ‘lots of weird noises’ and ‘percussion processor’.

Of course, there are many other things I ought to be doing with my money: monitor speakers, a new mixer, MIDI controller, food, rent, etc. But: oooooh.

It’s not even that expensive.


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