Pure Data: Electronic Music and Sound Design 1

INTRODUCTION

This is the first of a series of volumes dedicated to digital synthesis and sound design. The next volumes will cover a range of additional topics in the realm of sound synthesis and signal processing, including dynamics processing, delay lines, reverberation and spatialization, digital audio and sampled sounds, MIDI, non-linear techniques (such as AM, FM and wave terrain synthesis), granular synthesis and granulation, analysis and resynthesis, convolution, and computer-aided composition.

PREREQUISITES
This first volume will be useful to several levels of reader. Prerequisites for its study are minimal, and include nothing more than rudimentary musical knowledge such as an understanding of notes, scales, and chords, as well as basic computer skills such as saving files, copying and pasting text.
The volume should be equally useful for self-learners and for those studying under the guidance of a teacher. It is laid out as chapters of theoretical background material that are interleaved with chapters that contain practical computer techniques. Each pair of chapters stands together as a unit. We suggest that curricula follow this structure, first touching on theory, then following up with hands-on material, including computer activities. The theoretical chapters are not intended to substitute for more expansive texts about synthesis; they provide, instead, an organic framework for learning the theory that is needed to invent sounds on the computer and to write signal processing programs.

THE INTERACTIVE EXAMPLES
The path laid out in the theoretical sections of this book is meant to be accompanied by numerous interactive examples, which are available on the website at the support page for this text. Using these examples, the reader can immediately refer to the example sounds being discussed, as well as their design and elaboration, without having to spend intervening time on the practical work of programming. In this way, the study of theory can be immediately connected to the concrete experience of sounds. The integration of understanding and experience in the study of sound design and electronic music is our objective. This principle is the basis for the entire set of three volumes, as well as for future online materials that will help to update, broaden, and clarify the existing text.

THEORY AND PRACTICE
As we just said, the teaching approach for this book is based, first and foremost, upon an interplay between theory and practice, which we believe is indispensable. One of the glaring problems in the field of digital sound processing is the knowledge gap that exists between experts in theory (who often have neither the time nor the need to tackle concrete technical problems that are so relevant to the actual practice of creating sound) and those enthusiasts, much more numerous, who love to invent and modify sounds using their computers. These enthusiasts persevere, despite gaps in their theoretical awareness and/or in their understanding of how sounds may be modified within the rigid confines forced upon them by their specific software. It is our intention help these users of music software to acquire the deeper understanding that will take them beyond the confines of specific software to access the profound power inherent in the medium.

TEACHING APPROACH AND METHOD OF THIS BOOK
On the basis of the problems and concepts described above, we have tried to fill the information gap by continuing in the direction already begun with the book titled “Virtual Sound” (Cipriani and Bianchini, 2000), also dedicated to sound synthesis and signal processing. The innovations in this new text are substantial, with regard to both the examples provided and a completely different teaching approach. Because very little academic literature is available concerning methods for teaching electronic music, we have approached the problem directly, considering various promising ways to plumb the depths of the subject material. This exercise has led us to an organic teaching method, in which we adopt various ideas and techniques from foreign language textbooks in order to develop a more context- based, open-ended and interactive concept of teaching and learning. In addition to interactive examples, we have included “learning agendas” that detail the specific objectives for each chapter, that include listening and analysis activities, exercises and tests, glossaries, and suggestions for recordings to which to listen. The practical chapters of the book also include many other new features and activities, including the correction, completion, implementation, debugging, testing and analysis of algorithms, the construction of new algorithms from scratch, the replacement of parts of pre-built algorithms, and reverse engineering (in which the reader listens to a sound and then tries to invent an algorithm to create a similar sound). These activities and tasks are intended to activate the knowledge and practical skills of the reader. When learning a foreign language, there is a gap between what one knows and what one is able to use in practice. It is common for a student’s passive vocabulary (the total number of terms that the student can recognize) to be much larger than the active vocabulary that he or she can actually use while speaking or writing. The same is true of a programming language: a student can understand how algorithms work without being able to build them from scratch. The activities in this book that concentrate on replacing parts of algorithms, completing unfinished algorithms, correcting algorithms with bugs, and reverse engineering, have been included in order to pose problems to which the reader is encouraged to find his or her own solutions, causing the learning process to become more active and creative.
When learning a foreign language, students are given replacement exercises (e.g. “replace the underlined verb in the following phrase: I wish I could go out”), correction exercises (e.g. “correct the following phrase: I want to went home”), and sentences to be completed (e.g. “I’d like to … home”). In this context, it is vitally important for the student to work at these activities in order to avoid an excessively passive approach to learning. Our approach, likewise, not only involves interactions between the perception of sounds and the knowledge deriving from reading the book and doing the practical activities, but also interactions between these two factors and the user’s own skills and creativity.
This method is not based on a rigidly linear progression, but is rather a network that enables the reader to acquire knowledge and practical skills through an interaction of four separate dimensions: learning of the theoretical concepts, learning to use the Pure Data program, interacting with example material, and constructing algorithms.
This text is based on the book “Electronic Music and Sound Design – Theory and Practice with Max 8” by A. Cipriani and M.Giri, whose structure and educational vocation are maintained. The section dedicated to practice, where the techniques described in the theory chapters are exemplified, refers to the software Pure Data, which (just like Max) was created by Miller Puckette, and shares the general settings and many other features with Max.
Pure Data is a visual programming language, that allows you to connect graphic objects. These objects, which can perform calculations or process audio signals, can be connected to create very complex entities such as synthesizers and signal processors, or even authentic automatic sound devices.
Pure Data is free and open source. It can be downloaded for free and used on the most common operating systems. You can also modify the source code in order to create custom versions of the software. This set of features has led to the birth of an ever-growing community of musicians, programmers, and enthusiasts, and even to some interesting projects, such as Pd-extended (which, unfortunately, is no longer updated, and that, before ceasing to exist, was the reference version of the community). Hence, this book deals with the original version of Pure Data (sometimes referred to as Pd-vanilla), which is currently kept up-to-date and supported by Miller Puckette himself. The advantage of the vanilla version is that it ensures the compatibility with every platform, and most importantly, a longer continuity over time than the alternative versions.
The vanilla version of the software contains a rather small native-object library, and for this reason this book is accompanied with a library of abstractions (which are objects created within the environment, i.e.: made up of already- existing Pd objects) that allows you to boost the features of the program and to easily perform all those operations that would otherwise be really difficult to carry out (especially for a newbie who has just started learning the basics).

PRACTICAL INFORMATION
Many indispensable materials accompany this book, among them, interactive examples, patches (programs written in Pure Data), sound files, programming libraries, and other materials.
These can be found at the support page for this text.

Interactive Examples
During the study of a theory chapter, before moving on to the related practical chapter, it will help to use the interactive examples or video examples. Working with these examples will aid in the assimilation of the concepts raised by the theory.

Example Files
The example files (patches), are created to be used with Pure Data, which is freely downloadable from Miller Puckette’s site http://msp.ucsd.edu/software. html. As we have already mentioned, the book deals with the vanilla version (without extensions) of Pure Data.

Alternating Theory and Practice
In this book, theoretical chapters alternate with chapters which are geared towards programming practice. Because of this, the reader will find himself taking on all of the theory for a given chapter before passing to the corresponding practical chapter. An alternative to this approach would be to read a single section from the theory, and then go directly to the corresponding section of the practical chapter. (For example, 1.1T and 1.1P, then 1.2T and 1.2P, etc.

The Interludes
Note that there are two “technical interludes”, the first between the first and second chapters, and the second between the third and fourth chapters. These interludes, named respectively “Interlude A” and “Interlude B”, are dedicated specifically to the Pure Data language. They don’t relate directly to any of the theoretical discussions, but they are very necessary for following the code traced out in the book. After having tackled the theory and practice of the first chapter, before moving on to the second chapter, it will benefit the reader to study Interlude A. Likewise, Interlude B is meant to be studied between Chapters 3 and 4.

Learning Pure Data
Learning Pure Data (and, in general, learning synthesis and sound processing) requires effort and concentration. In contrast to much commercial music software, Pure Data provides flexibility to the programmer, and this design choice provides those programming with Pd many alternative ways to build a given algorithm. To benefit from this the recommendations of the book and to code in a systematic way. Pd is a true musical instrument, and learning to play it should be approached as one would approach the study of a traditional instrument (such as a violin). As with any instrument, the reader will find it necessary to practice regularly, and to stay sharp on basics while gradually acquiring more complex techniques. By approaching the software in this way, fundamental techniques and technical insights can be retained once they have been acquired.

Bibliography
The decision was made to limit the bibliography in this book to a list of only the most absolutely essential reference works, and, of course, a list of the books and articles cited in the text. A more comprehensive bibliography is available online.

Before Beginning
To begin working with this book, you will need to download the interactive programming examples, which you will find at the support page for this text. While reading the theory chapters, you will find constant references to the examples contained in this downloadable archive. To work interactively with the programming chapters of the book, you will need to download the Virtual Sound Macro Library from the support page mentioned above. It will also be necessary to install Pure Data, which is available at Miller Puckette’s website: http://msp.ucsd.edu/software. html.
The support page for this text contains detailed instructions regarding how to install Pd and the macro library correctly. Always check the support page for patches (Pd programs) related to the practice chapters of this book, as well as the audio files for the reverse engineering exercises.