anthony mattox new media art & design

Pure Data: My First Attempts at Virtual Instruments

For a while I’ve been interested in exploring sound as a new medium. Pure Data is a sound program which I’ve been particularly interested in. The program is something like a visual programming language, with a similar interface to quartz composer. Objects which represent chunks of code are placed on the canvas. These objects have inputs and outputs through which they send and receive data in the form of numbers, strings, and audio signals. Some graphic interface elements call also be added to control applications.

Starting to work with Pure Data is a little intimidating. Objects added to the stage are blank and you have to type into them what object the should be. Until you understand what the basic objects are and how they interact trying to get anything working isn’t easy. For at least a good while I’ve been opening up Pure Data every few months only to put it away again after beating my head against it for a while.

For my recent flash game, Pulsus, I decided to create the sound using Pure Data to force myself to learn the program. I managed to cobble together a basic understanding and build a few synthesizers and sound generators.

I used this first patch to create most of the sound effects in the game. For a number of oscillators the pitch and envelope can be changed. The pitches can create harmonics, harmonies, or dissonant chords. The envelope, the volume over the course of the sound, creates pulsing tones, short beats, and any other type of tone. I also added an amplitude modulator and a global envelope to add some more control.

In my next experiment I created a simple mono synthesizer. Key inputs, from my computer keyboard, are mapped into midi notes. When a key is pressed the frequency slides to that note if another note is still playing. Key presses trigger the envelope generator which reads data from an array (top right). The synth also has frequency and amplitude modulators and reads the waveform from a table to include harmonics.

Next I build a polyphonic synthesizer which has a separate oscillator for every note in the scale.

Here are the pure data files for these patches in case they might be useful to anyone, but again they are not super efficient, organized, or annotated.

• tone generator
• monosynth
• polysynth
• polysynth tone (an abstract for the polysynth)

These are my first moderately successful explorations with Pure Data. Some things, I realize, are not done as efficiently as possible, but I’m working things out in the next iteration. My next frustration is to find a way to control the instruments I build. I need a midi sequencer with which I can construct songs that could then send the midi info to Pure Data. I tried using a garage band plugin to output midi info from garage band but It came out pretty garbled in PD, I could be doing something wrong though. Any thoughts on how I should go about this?

Arduino Synthesizer

I’ve been interested in experimenting with electronic music for a while now and also recently started doing some work with the Arduino. So I thought, ‘why not try both?’ I began with a great article I found on Make Magazine (one of my absolute favorite sites) to create the basic script to generate an audio signal with an Arduino. A Digital to Analog Converter (DAC) converts the binary outputs from the Arduino into a relatively fluid scale of voltages which make up the sound wave

On the electronics side, my setup is quite similar to my reference, with the addition of a small amplifier using an LM386 op amp chip and a couple resistors and capacitors for some basic filtering. On the code side I’ve created a much more substantial instrument. Using Processing I built an interface to create a 32 sample waveform and a melody. The data is sent live to the Arduino which places the data into it’s waveform array and then using a timer writes each value sequentially to the DAC to create the sound.

The interface contains two sets of sliders. One represents the shape of the sound wave. Changing the shape alters the timbre of the sound. The second set controls a series of pitches. The currently playing note is lit and a light bar indicates the current position of the playhead. The waveform sliders can be adjusted individually or as a group by clicking and dragging across the set. The sequence bars control both the pitch and the frequency of the notes.