1. Developing Software Synthesizers
By: Dan Bogucki

2. Overview What is Sound? What is a Sound Synthesizer?
History of the Synthesizer
Hardware vs. Software
Why turn to Software Synthesizer?
Types of Synthesizers Methodology
The Makeup of a Synthesizer
Developing a Software Synthesizer

3. What is Sound?
Sound is moving energy that travels as a pattern of changing pressure
Sound is the perceived vibration (oscillation) of air resulting from the vibration of a sound source
Sound source can be anything
Guitar sound board, speaker cone, hair dryer, vocal cord, etc

4. Sound Waves
As your sound source expands and contracts a pattern of changing air pressure energy moves away from the source
Ottewill, Matt. "What Is Sound?" Planet Of Tunes. N.p., n.d. Web. 13 Mar

5. Sound Waves Four Types of basic waveforms Sine Square Sawtooth
Triangle

6. Sound Waves

7. What is a Sound Synthesizer?
An electronic instrument capable of producing sound
Generate electric signals (waveforms) which are converted to sound through speakers or headphones

8. History of the Synthesizer
1860 – Hermann von Helmholtz built an electro-mechanical oscillator
1906 – Lee de Forest invented a vacuum-triode amplifier valve
1950s – Transistors became available
1961 – Harald Bode invented the Melochord, the first voltage controlled synthesizer
1964 – Robert Moog constructed a transistor voltage-controlled oscillator and amplifier
1966 – Moog launched the first commercial version of the Moog Synthesizer

9. History Continued
1950s – Max Mathews of Bell Telephone Lab began exploring the use of using digital computers as a means to generate sounds.
Mathews produced MUSIC III
1962 – MUSIC IV
1968 – MUSIC V
1968 – Barry Vercoe developed MUSIC 360
1973 – Vercoe developed MUSIC11
1979 – Australian Fairlight CMI synthesizer was introduced

10. Hardware vs. Software Software synthesizers use digital processors
Hardware synthesizers use analog circuitry
Computer technology is advancing faster than hardware synthesizer technology
For example, wavetable and additive synthesis is not feasible with hardware synthesizers
Musicians preference between hardware sounds and character vs. software sounds

11. Why Turn to Software Synthesizers?
Popularity of personal computers
More flexibility and invention for both the end user as well as the software itself
Cost

12. Software Synthesizer Example

13. Synthesizer Methodology
Additive Synthesis
Subtractive Synthesis
FM Synthesis
Wavetable Synthesis

14. Additive Synthesis Most fundamental method of sound synthesis
Based on the Fourier Theory
Produces sound by adding different sine waveforms together
This technique can potentially generate sounds similar to acoustic musical instruments

15. Subtractive Synthesis
Basically the reverse of additive synthesis
Produces sounds by generating a waveform that contains more harmonic content than a sine wave
The waveform is passed through filters which subtract harmonics

16. FM Synthesis Uses FM sidebands as harmonics for synthesized waveforms.
Applied digitally through FM operators
Digital sine waveform and an envelope
Output is then used to modulate the frequency of another operator
Modulation of one sine wave by another produces more complex sounds
Used widely in radio transmission

17. Wavetable Synthesis Also known as sampling
Most widespread and popular method
Recorded or synthesized musical events are stored in the internal memory and are played back on demand
Provides a set of playback tools
Pitch Shifting
Looping
Enveloping

18. General Makeup of a Synthesizer Today
Oscillators
Envelopes
Filters
Frequency Modulators
Samplers (in some synthesizers)
Functionality and options are endless

19. Oscillators
Control to repeat a waveform with a fundamental frequency and peak amplitude

20. Envelopes The synthesizer’s time varying gain function
Simple analogy: A sequence of events that occurs every time you press a key
Attack
Decay
Sustain
Release

21. Filters Subtract frequency content Behave like an equalizer
Four basic types
Low-pass
High-pass
Band-pass
Band-reject

22. Developing a Software Synthesizer
To create sound we need to move an object. In this case a speaker or headphones
Formula for generating a sine wave is
Y = sin(x)
Simple right?

23. Developing a Software Synthesizer
Many programming languages have standard mathematics libraries with many of the trigonometric functions represented
Most basic computer synthesis methods follow this same general scheme: a formula or function is defined that accepts a sequence of values as input

24. Developing a Software Synthesizer
Computer soundcards have digital-to-analog converters
They are able to generate an electrical signal from a digital number that is given to it

25. Producing a Simple Sine Wave
A cycle of a sine wave is 2π radians long
Sine waves have a peak amplitude of +/- 1
A sample rate would be cycles per second – range of the entire human ear

26. Producing a Simple Sine Wave
Input: Peak amplitude (A), Frequency (f) Output: Amplitude value (y)
y = A * sin(phase)
phase = phase + ((2 * pi * f) / samplerate)
if phase > (2 * pi) then
phase = phase - (2 * pi)

27. Producing a Square Wave
Input: Peak amplitude (A), Frequency (f)
Output: Amplitude value (y)
if phase < pi then
y = A
else
y = -A
phase = phase + ((2 * pi * f) / samplerate)
if phase > (2 * pi) then
phase = phase - (2 * pi)

28. Virtual Studio Technology (VST)
Interface for integrating software audio synthesizer and effect plugins with audio editors
Use digital signal processing
VST is supported by a large number of audio applications

29. Virtual Studio Technology (VST)
Run within your Digital Audio Workstation (DAW)
Classified as instruments or effects
VST instruments include synthesizers and samplers
VST effects include effects like reverb and phaser
First released in 1996

30. Virtual Studio Technology (VST)
VST is the plugin standard for DAWs
Allows any third party developer to create a VST plugin for use within DAWs
Steinberg’s VST SDK is a set of C++ classes based around an underlying C API.
You can download the SDK from their website
Steinberg also developed the VST GUI (another set of C++ classes) which is also available to add graphical interface to your VST

31. Virtual Studio Technology (VST)
There are several third party ports available
jVSTwRapper – Java version
Python ctypes-based VST wrapper
Noise and VST.NET – two .NET versions
LADSPA – Linux Audio Developers Simple Plugin API
JRUBY
And many more!

32. Virtual Studio Technology (VST)
LADSPA Header File

33. Questions / Comments?

34. References
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35. References
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36. "DrPetter's Homepage - Basic Sound. Theory and Synthesis. " DrPetter's
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