Sound Synthesis and Virtual Instruments - Common Terms Explained

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audio midi setupVirtual instruments play a significant role in the vast majority of the music made today.  With the ever-increasing processing power of computers, software synthesizers have become an extremely capable, convenient, and affordable option for the recording artist in comparison with the field's predecessors.  This article summarizes the fundamentals of sound synthesis, some of the commonly-used and associated terms, and how it is predominantly incorporated into many modern recording environments.


Basic Introduction to the Synthesis of Sound

The advent of the synthesizer, and development of the resulting techniques, have served key roles in broadening the scope of sonic possibilities in music production and audio design practices.  For all intents and purposes of this article, the term "synthesis" refers to the creation of sound by way of an electronic means.

In the synthesis of sound, various analog devices, and in turn numerous algorithms modeled after them, are used to generate, modify, and amplify electrical signals.  Let us begin by taking a brief look at a few of the different types, and some of the terminology you will encounter.

A number of terms are used to describe the comprising elements and their involvement in this "musical manufacturing process" of sorts.  The following aims to provide a a technical explanation of some of the fundamental concepts involved, and a basic overview of the primary methods being used


  • VCO: Voltage-Controlled Oscillator - An electronic device that creates the rhythmic and repetitious signal, referred to as an oscillation, most commonly used as the point of origination and overall basis for the sound being created.

  • Frequency - A measurement of the rate at which the aforementioned device operates.  This dictates what is perceived as musical pitch, and is calculated in terms of Hertz (Hz), or cycles per second.

  • VCF: Voltage-Controlled Filter - A modifier used to alter the harmonic content of the sound, by removing a portion of the spectrum of frequencies produced by the oscillator(s).

  • LFO: Low Frequency Oscillator - An LFO generally operates at or below 20Hz, which happens to be the absolute "ground level" if talking about the range of human hearing. 

Question: "So how can this be used in the creation of music and sound, if we are unable to actually hear it?"

Often assigned to control parameters such as amplitude, pitch, and frequency of an oscillator or filter, this type of device is primarily used to add pulsating and rhythmic alterations in the tone.  what this allows us to hear, when properly applied, is not simply the tone it has in its particular movement through space and time.  instead, this creates audible fluctuations and modifications of the signal, ranging from subtle to surreal.

  • Waveform - Formation of a waves; the visual representation of the shape and tonality of acoustic energy in relation to time.

  • ADSR (Attack Decay Sustain Release)Envelope - Definable shape and general evolution of the sound from beginning to end.
    • Attack -Time required for the envelope to reach its peak level.
    • Decay -Time from this initial peak until the level begins to drop.
    • Sustain - Level of the signal after the decay maintained until released.
    • Release -Time required for the level to return to its initial zero value.

Popular Styles

  • Additive Synthesis - Creation of sounds through the combination, or adding together, of harmonically-related waveforms, 

  • Subtractive Synthesis - The art of carving and sculpting a sound and its desired instrumental characteristics from simple, yet musically-rich waveforms using oscillators and filters.

  • FM Synthesis - Shorthand for frequency modulation synthesis, this is the process of using one or more sinusoidal oscillators, known as  operators, in defining the musical characteristics and amplitude of a fundamental sine wave carrier signal.

  • Sampling - The application of synthesis techniques to the playing back of recorded audio clips.  This technique is most commonly observed and practiced in the areas of hip hop, turntablism, and the majority of electronic music production.

Virtual Instruments, MIDI Controllers, & Modern Product Development 

Virtual Instruments are essentially nothing more than the digital embodiment of analog instruments and synthesizers, by way of computer programming and digital signal processing, or DSP.  Technologies conceived and developed over the course of the last century or so have evolved into a representation of the mechanics of sound through collection of samples and the arrangement of data.  

Software companies now have a greater ability to direct more efforts and expenditures towards research and development rather than costly manufacturing processes.  This  has resulted in some remarkably powerful and explorative tools for the modern musician, with the portability and a price tag that almost anyone can manage.  As efforts in computer advancement continues, so will the creation of instruments and audio processing technologies for years to come.  Be sure to visit the following pages for some examples of available instruments and performance controllers.

  • AIR Music Technology - One of the earliest pioneers in virtual instrument technology, AIR’s mission is to create the world’s most innovative virtual instruments, music software and effects.
  • Akai Professional - Iconic MPC Series of sequencers, samplers, and performance controllers.  Innovative pad controllers, keyboards, recording devices, and electronic wind instruments.
  • Alesis - Advanced yet affordable full line of electronic percussion products, highly innovative and adaptable computer audio interfaces and controllers.  Founded on innovative semi-conductor chip technology and award winning industrial designs.

  • M-Audio - Best-selling keyboard controllers, audio & MIDI interfaces, and studio monitors.

  • SONiVOX - Products for professional composers, producers, musicians, and iPad and Android developers.

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