CCRMA Music 250a Physical Interaction Design, Winter 2006

Lab 1: Mappings, Modes, Sound Generation, Pd

Matt Wright, June 27, 2005
updated by Bill Verplank, , 2005

1. Set up your CCRMA account

Get a CCRMA Linux account.

Learn how to open a terminal window, a web browser, and Pd.

Add these lines to the .pdrc file in your home directory:

-path /usr/ccrma/courses/250a/pd/externs 
-path /usr/ccrma/courses/250a/pd/patches
-alsa -midiindev 2 -midioutdev 2 
-lib OSC -lib zexy -lib percolate

2. Download today's simple QWERTY sample triggering patch

Copy my Pd patches and the associated sound files to your 250a/lab1 directory, and open the main patch lab1.pd:

cd
mkdir 250a
cd 250a
cp -r /usr/ccrma/web/html/courses/250a/labs/lab1/lab1.tar .
tar -xvf lab1.tar 

cd lab1
pd qwerty.pd

Play around with this patch. You should be able to exhaust its musical potential in a matter of minutes; reflect on its strengths and limitations.

Also try to understand how it works as a piece of software. (But please don't get hung up on the Pd as always, if you get stuck, ask for help rather than waste time.)

Pd Documentation

Right-click on any object to get a contextual menu including "help," which opens that object's help patch.

Right-click on a blank portion of a Pd patch. Now when you select "help" you get a list of Pd's built-in objects, arranged by category.

In the upper right hand corner of each Pd window is a "help" menu. This accesses the Pd tutorials as well as some online reference documentation.

3. Sample Triggering (qwerty) Patch

The problem with using the operating system's automatic "key repeat" feature for musical control is that you don't have good control of timing. There are actually two "time constants" involved: the time between when you first press the key and it starts repeating, and then time time between repetitions.

Re-implement the "key repeat" feature in Pd so that you have complete control of the two time constants (as well as being to enable and disable the feature). You will probably need to use Pd's "metro", "delay", and "spigot" objects.

4. Design a different musical interaction for qwerty.pd

Here are some ideas of changes that might make the patch more interesting:

• Involve more QWERTY keys
• Load in a larger collection of samples.
  • Implement a mechanism to switch among banks of samples
• Multiple gestures to one result: design a way for the parameters of each triggered note to depend on multiple keypresses. For example, maybe only the space bar triggers notes, and all the other keys determine parameters of notes.
  • Set multiple parameters modally, as volume works in the sample patch
  • Use "chording": keep track of all the keys that are currently pressed, and use only that information to set the parameters for each note.
• One gesture to multiple results
  • Use Pd's "metro" object to trigger a steady stream of notes. Now you have two new parameters: repetition rate, and whether the metro is on or off.
  • Use Pd's "counter" object to step through a cycle (of samples, parameter settings, etc.)
  • You could combine "metro" and "counter" to build a rudimentary sequencer that can step through a rhythmic pattern
  • Invent a mechanism to record short sequences of keypresses and play them back in time.
• Use Pd's "spigot" object to route control information to different parts of your patch at different times
• Use some additional signal processing such as a filter, delay line, reverb, tremolo, etc. This gives you more parameters to control.
• Polyphony: make it so the patch can play multiple samples at the same time. (Hint: put multiple copies of "play-sample" in your patch, then use
• Use a totally different form of sound synthesis, such as FM, granular, or physical modeling.

We recommend that you pick one or a small number of these and work on it in depth, iterating on both the program/test/debug cycle as well as the design/implement/play cycle to craft something that has actual musical potential or is at least more fun to play. If you have an existing idea for your class project, you could use this lab to start thinking about implementing some of the modes and mappings. By all means, if you're inspired to try something else, go for it. If you'd rather spend today getting more of a broad sense of Pd's capabilities, feel free to work on many of these suggestions.

5. Theremin

• Try "theremin.pd" as an example of using mouse position for musical control. It uses a "canvas" to get x,y position which you can see in "xy_canvas.pd".
• What is the purpose of the line~ object? Try bypassing it. What if the metro samples every 100 ms or 1000 ms (1 second intervals)? How might you combine key-presses with mouse motion?
• Save your work with a recognizable name like "mouse_music.pd" in your lab1 directory. Send a email with a one-line description for one or two of your favorite "experiments".

The Pd Community

Although Pd is clunky and has lots of usability issues, there is a large, dedicated, and very generous community of Pd users on the Internet. Do some web searching (e.g., with a search engine, or else starting from some Pd-specific resources) and look for interesting Pd externals and/or patches. Download, install, and play with at least one. Can you incorporate it into what you programmed in part 4?