Table Of ContentDesigning Software Synthesizer Plugins in C++
Designing Software Synthesizer Plugins in C++ provides everything you need to know to start
designing and writing your own synthesizer plugins, including theory and practical examples for
all of the major synthesizer building blocks, from LFOs and EGs to PCM samples and morphing
wavetables, along with complete synthesizer example projects.
The book and accompanying SynthLab projects include scores of C++ objects and functions
that implement the synthesizer building blocks as well as six synthesizer projects, ranging from
virtual analog and physical modelling to wavetable morphing and wave-sequencing that demon-
strate their use. You can start using the book immediately with the SynthLab-DM product, which
allows you to compile and load mini-modules that resemble modular synth components without
needing to maintain the complete synth project code. The C++ objects all run in a stand-alone
mode, so you can incorporate them into your current projects or whip up a quick experiment. All
six synth projects are fully documented, from the tiny SynthClock to the SynthEngine objects, al-
lowing you to get the most from the book while working at a level that you feel comfortable with.
This book is intended for music technology and engineering students, along with DIY audio
programmers and anyone wanting to understand how synthesizers may be implemented in C++.
Will C. Pirkle is a Staff Scientist at Audio Media Research, Inc. and Music Engineering Technol-
ogy program director at the University of Miami Frost School of Music. He teaches a range of
classes, from audio electronics to digital signal processing and audio programming. In addition to
16 years of teaching, Will has 20+ years of experience in the audio industry, working and consult-
ing for such names as Korg Research and Development, XM Radio, and National Semiconductor
Corporation. An avid guitarist and studio owner, Will enjoys projects that combine his skills.
Taylor & Francis
Taylor & Francis Group
http://taylorandfrancis.com
Designing Software Synthesizer
Plugins in C++
With Audio DSP
2nd Edition
Will C. Pirkle
First published 2021
by Routledge
605 Third Avenue, New York, NY 10158
and by Routledge
2 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN
Routledge is an imprint of the Taylor & Francis Group, an informa business
© 2021 Will C. Pirkle
The right of Will C. Pirkle to be identified as author of this work has been asserted by him in
accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form
or by any electronic, mechanical, or other means, now known or hereafter invented, including
photocopying and recording, or in any information storage or retrieval system, without
permission in writing from the publishers.
Trademark notice: Product or corporate names may be trademarks or registered trademarks,
and are used only for identification and explanation without intent to infringe.
Library of Congress Cataloging-in-Publication Data
A catalog record for this title has been requested
ISBN: 978-0-367-51048-0 (hbk)
ISBN: 978-0-367-51046-6 (pbk)
ISBN: 978-1-003-05220-3 (ebk)
Typeset in Times New Roman
by codeMantra
James Robert Pirkle
Taylor & Francis
Taylor & Francis Group
http://taylorandfrancis.com
Contents
List of Figures xiii
List of Tables xxiii
Preface xxv
1 SynthLab Introduction 1
1.1 What You Need to Know to Use SynthLab Objects and Projects 2
1.2 SynthLab Synth Projects 2
1.3 Synth Components 3
1.4 Basic Software Synth Architecture 4
1.5 SynthLab Voice Architecture 4
1.6 SynthLab C++ Implementation 5
1.7 Why SynthLab Uses This Architecture 8
1.8 SynthLab Object Operational Phases 9
Bibliography 11
2 The Synth Engine 12
2.1 Engine Behavior 12
2.2 Engine Architecture 12
2.3 Shared Data 13
2.4 SynthEngine Constructor 18
2.5 Audio and MIDI Block Rendering 18
2.6 SynthEngine Operational Phases 20
Bibliography 26
3 Synth Voices, Synth Modules, and Module Cores 27
3.1 Voice Behavior 27
3.2 SynthVoice Modules 27
3.3 SynthVoice Parameters 28
3.4 SynthModule Members 29
3.5 SynthVoice Construction 30
viii Contents
3.6 SynthVoice Operational Phases 31
3.7 SynthModules and ModuleCores 35
3.8 Module Cores 37
3.9 SynthModule/ModuleCore Relationship 37
3.10 Review 41
Bibliography 41
4 Synth Operational Modes: Polyphony and Voice-Stealing 42
4.1 The Note-Event Lifecycle 43
4.2 SynthEngine MIDI Processing 44
4.3 SynthEngine Unison Detuning 46
4.4 Voice State and MIDI Event Storage 47
4.5 Voice-Stealing 47
4.6 Polyphony and Voice Timestamps 50
4.7 Review 53
Bibliography 53
5 Learning and Using the SynthLab Objects & Projects 54
5.1 Designing Modules with the SynthLab-DM Projects 54
5.2 SynthLab-DM Modules Are Dynamic Linked Libraries 54
5.3 Using SynthModules in Your Projects 58
5.4 Using SynthEngines in Your Projects 63
5.5 SynthEngine GUI Design and Parameter Update 66
5.6 Programming the Modulation Matrix 69
5.7 Getting WaveSequencer Status Meter Updates 69
Bibliography 69
6 Modulation: Theory and Calculations 70
6.1 SynthLab Mod Knob Mapping 70
6.2 MMA Transforms & Calculations 71
6.3 Sequential Circuits Vector Joystick Envelope Modulation 74
6.4 Linear Frequency Modulation with LFO or EG 75
6.5 BPM Sync 76
6.6 Quantizing 77
6.7 Ramp Modulation: Fade-in and Fade-out 77
6.8 Pitch Calculation 79
6.9 Pulse-Width Modulation (PWM) 81
6.10 Phase Distortion 81
6.11 Hard Sync 83
6.12 Filter Key Track Modulation 85
Bibliography 86
Contents ix
7 Envelope Generators and DCA 87
7.1 Envelope Generator Fundamentals 87
7.2 EG Implementation: Finite State Machine 92
7.3 Digital EG Implementation: Rendering the Output 95
7.4 Biased EG Output 96
7.5 Analog EG Emulation 97
7.6 Synth Module: EnvelopeGenerator 100
7.7 EG Retrigger Modulation 101
7.8 EG Core Programming Notes 102
7.9 The Digitally Controlled Amplifier (DCA) 106
7.10 Exercises 108
Bibliography 109
8 Low Frequency Oscillators 110
8.1 Noise Oscillators and Generators 110
8.2 Oscillator Clocking 111
8.3 LFO Waveforms and Rendering Equations 112
8.4 Render Modes 116
8.5 Waveform Shaping 117
8.6 Delay and Fade-in Times 117
8.7 Starting Phase 117
8.8 DC Offset 117
8.9 SynthLFO and Cores 118
8.10 LFO Core Programming Notes 119
8.11 Exercises 121
Bibliography 123
9 Wavetable Oscillators 124
9.1 Wavetable Fundamentals: Table Lookup 124
9.2 Wavetable Objects and Database 130
9.3 Wavetable Sources and Database 131
9.4 WTOscillator and Cores 134
9.5 Wavetable Core Programming Notes 135
9.6 Exercises 139
Bibliography 140
10 Virtual Analog Oscillators 141
10.1 VA Oscillator Fundamentals 141
10.2 Band Limited Impulse Train (BLIT) 142
10.3 Band Limited Step (BLEP) 143
