Music 250 - Winter 2005
Human Computer Interaction Theory and Practice: Designing New Devices

A Short Guide to Pd & OSC (1/19/05)

Introduction

Instruction

Run & new patch

1. Run Pd (Main Menu - Sound & Video - Pd, or just type pd in a terminal)
2. Make a new patch (File - New, or ctrl-n)
3. In the patch window, we can create a new object (Put - Object, or ctrl-1). You can specify the type of object by typing its name (to see the list of "object" classes, right-click on the "canvas" and choose "Help").

Noise generator

1. To make a noise generator, we need a noise object. Type "noise~" and click outside the object box to 'activate' it.
   The "~" at the end of the name means it's working at audio frequency rate.
   
2. And to hear the sound, a digital-to-analog converter is needed. Put another object named "dac~" the same way.
   
3. By dragging the mouse, connect the bottom-left corner of "noise~" (which is the output of the object) to top-left of "dac~" (the input to the left channel of the DAC). Notice that the cursor turns into a small circle when placed on the "nodes".
   
4. Turn on the audio (Audio - On, or ctrl-/), and check the noise coming from left channel.
   (If you want the same noise coming from both channels, make another connection from the "noise~" object to the top-right of "dac~".
   

Sinusoidal oscillator

1. Now we need an oscillator, not a noise generator.
   Convert the noise object into a sinusoidal oscillator; rename it as "osc~".
   
   It has two inputs and one output.
   To get more information about them, see the "Help" in its patch by right-clicking on the object and choosing "Help".
   
   Now you know that the left one is for frequency, the right one for phase (which we won't care within this tutorial).
2. Turn the audio on. Since you didn't put any frequency value to the oscillator, you won't hear any sound by now.
3. Let's specify the frequency; put a "Number" (Put - Number, or ctrl-3), and connect its output to the frequency input (left) of the "osc~".
   
4. Now get out of the edit mode (Edit - Edit Mode, or ctrl-e), and change the value of the number object (that is, oscillator frequency) by drag-n-dropping the mouse over it. You should be able to hear the sound (BTW, this is a very good patch to test your hearing ability in terms of pitch ;> ).
   

(Probably the simplest) additive synthesis patch

1. Now we need one more oscillator(s), add their outputs, and send it to DAC.
   First, make sure you're back in the Edit mode.
2. Disconnect the oscillator from the DAC; select the connection by mouse and press "Delete".
   
3. Copy the number and the oscillator set; select them by mouse and Edit - Copy (or ctrl-c).
4. Paste them, and move it away from the original one.
   
5. Now add the outputs of those oscillators
   Put a new object, name it as "+~". Make connections from each oscillator to the inputs of the adder. Also, connect its output to DAC.
   
6. Get out of the edit mode, and change the frequencies the same way.
7. Question: what will happen if we use "*~" instead of "+~"?
   

Examples

• tutorial_1.pd
• tutorial_2.pd

OSC: OpenSound Control

• OpenSound Control of class material page.
• Introduction
• OSC (and especially OSC address spaces) as a good way to organize software even without network communication:
• A brief intro to OSC
• OSC Application Areas

Using OSC in Pd

1. OSC object: load OSC library.
2. sendOSC object: to send out OSC data
3. dumpOSC object: to receive OSC data
4. dumpOSCSerial object: to receive OSC data through serial port
5. OSCRoute object: to route incoming OSC data based on their address space

References

• the official Pd documentation
• the official home of OSC at CNMAT
  
  
• Curtis Roads, The Computer Music Tutorial, MIT Press (ISBN 0-262-68082-3)
• Additive Synthesis (also look: Introduction to Sound Synthesis)
• Sound Synthesis Methods
• Sound Synthesis