C.S. Graves

After having written my article on sample start modulation for issue one, it was suggested to me that I should have explained all the terms for the benefit of the uninitiated. I considered this, but concluded that it would have weighed down the article, and the constant digression into such explanations would have added further confusion to it. It would have to be assumed that my readers had a basic knowledge of synthesis for the piece to be quick and efficient. But the initial suggestion warranted an article of its own, and this is it. I will attempt to shed light on many of the most common technical terms used in synthesis today, so that the beginner may have some grasp on the concepts that will no doubt arise throughout the lifespan of this publication. You'll have to do a lot of jumping from one term to another and back again, so if you don't understand a word or two, look through the list and see if they are defined.

808 - from Roland's TR-808 drum machine. Often used to refer to the characteristic synthetic drums sounds produced by the 808.
Additive - the method of synthesis where numerous sine waves are added to a fundamental frequency. Theoretically any sound can be recreated using additive synthesis, but the sheer number of partials in a complex sound require tremendous computational power. The most familiar use of simple additive synthesis is in Hammond organs and the like.
ADSR - abbreviation for ATTACK DECAY SUSTAIN RELEASE. The prototypical envelope invented by Vladimir Ussachevsky for early Moog synthesizers.
Aftertouch - see Pressure.
Aliasing - in digital audio, the distortion that occurs when the frequencies of the source sound exceed the Nyquist frequency.
Amplitude - the extent or loudness of sound at any given time. Amplitude can be positive or negative.
Analog or Analogue - pre-digital method of synthesis that utilizes voltages to produce and process sound.
Analog Modelling - digital synthesis method designed to emulate analog synthesis.
Architecture - the setup and interaction of sound producing and processing components that dictates how sounds are synthesized on a given machine or piece of software.
Arpeggiator - a device which produces arpeggios at the touch of a key.
Attack - the initial stage of a sound. A fast or strong attack indicates immediacy, as in a loud burst of sound, while a slow or weak attack makes for a gradual increase, as in a crescendo or swelling.
Band-pass filter - a filter which only allows a defined spectrum of frequencies to pass.
Bit Resolution - the dynamic range possible in a digital audio format. The better the resolution, the more faithful the recording. Each bit rating is double the resolution of the rating immediately below it (8-bit = 2x7-bit)
Cancellation - when a positive and a negative amplitude cancel each other out.
Clipping - the distortion which occurs when the source sound exceeds the dynamic threshold of a digital recording.
Controller - either 1. a hardware device such as a keyboard used to control a synthesis device, 2. a component of a larger device used to control a specific aspect of the sounds, such as a mod wheel, or 3. a type of information sent by such devices or sequencers (e.g. velocity, volume, etc...).
Cross-fade - when one sound is faded out while another is faded in simultaneously. The intent is usually to create a seamless transition.
CV - abbr.: Control Voltage. Pretty self-explanatory. Control voltage is used to control some aspect of synthesis, such as pitch and filter cutoff on analog synths.
CV pedal - a control voltage pedal most often used to control volume, but can often be used to modulate other things.
Cycle - the smallest pattern within a waveform in which the amplitude starts at zero, travels through positive and negative values, and then returns to zero.
Decay - the stage in which some property of the sound decreases, such as the amplitude of a sound as it dies out.
Digital Synthesis - any method which relies on digital computers to produce sound.
DIN - pre-MIDI input/output standard for syncronizing drum machines and sequencers. Named for the 5-pin-DIN cable used to connect devices.
Drum Machine - device that produces drum sounds and rhythm patterns.
Duty cycle - in a pulse wave, the ratio of positive amplitude to wavelength expressed by a percentage.
Dynamic Range - the range between the softest and loudest sounds recordable by a medium.
Dynamic Threshold - the maximum amplitude recordable without distortion.
Emulative - synthesis intended to sound like, or emulate, a pre-existing instrument.
Envelope - a series of time values working in conjuction with modulation values. The ADSR evelope is the most well- known example.
Filter - to remove certain frequencies from a sound, or a device which performs this function.
Filter cutoff - the point where a filter ceases to affect sound frequencies.
FM - abbr.: Frequency Modulation. Method of synthesis where one oscillator modulates the frequency of another oscillator, called the carrier. Although technically even a low frequency modulator can be considered frequency modulation, the term FM is usually only applied when the modulator exceeds 30 Hz or so, and enters the audible range.
Gate - in analog synthesis, an audio signal which indicates when a key on the controller is being pressed and released. Gate controls the duration of notes played, much like MIDI Note on and Note off messages.
Hertz - a unit of measurement dealing with cycles per second, named after 19th century German physicist Heinrich Hertz. It can be used to express sound frequency and sample rate. It is subject to the prefixes used in the metric system (megahertz, kilohertz, etc...).
High-Pass Filter - a filter which removes low frequencies while allowing higher frequencies to pass.
Hz - see Hertz
LFO - abbr.: Low Frequency Oscillator. A modulator which when applied to pitch produces vibrato, and when applied to amplitude produces tremolo. LFO's can be any of the basic waveforms (see Sawtooth wave, Sinewave, Square wave, and triangle wave).
Loop - a section of a waveform that repeats itself. Loops are often used in sampling to conserve memory.
Low-Pass Filter - a filter which removes high frequencies while allowing low frequencies to pass.
MIDI - abbr.: Musical Instrument Digital Interface. A standard protocol invented in the 1980's to allow the interaction and control of multiple synthesis devices.
Mod Wheel - diminutive for Modulation Wheel. A wheel-like controller on a keyboard which can be used in performance to modulate elements of a synthetic sound. Most commonly used to control LFO depth.
Modular - method of synthesis where numerous modules are connected to produce sound. Modular synthesis has no fixed architecture and allows significant freedom for sound design. Most modular synthesizers are analog, but recently digital and software synthesizers have adopted the modular approach.
Modulation - to change any value or property of synthetic sound.
Monophonic - a synth where only one voice can sound at once.
Multitimbral - the ability of a synth to have multiple sounds play and be controlled separately.
Noise - a sound where various frequencies are present at any given time. White noise contains all frequencies, pink noise has less high frequencies than white, brown noise contains only low frequencies, and red noise is the result of white noise put through a band pass filter.
Nyquist Frequency - the highest frequency accurately reproduceable by digital means. It is one half of the sample rate of a digital recording.
Oscillator - a device which produces waveforms.
Pad - a gentle, sustaining sound often with a soft attack usually used to play chords in the background of a piece of music.
Pan - the position of a sound in stereo space.
Partial - one of the many pure tones (sinewaves) that make up a more complex waveform.
Patch - a synthesized sound, whether it's a single unprocessed oscillator, or many waveforms mixed together and heavily processed. The term comes from the patch cords used in modular synthesis.
PCM - abbr.: Pulse Code Modulation. Term indicating digital audio.
Physical Modelling - method of synthesis where mathematical algorithms are used to emulate the physical behaviour of acoustic instruments.
Polyphonic - a synth where multiple voices can sound at once.
Polyphony - the number of voices a device can play at once.
Preset - a patch or sound included with a synthesizer.
Pressure - the pressure exerted on a key after it is pressed.
Pulse wave - waveform where the transition from positive to negative amplitudes and back is very rapid. See also Square wave.
Pulse width - the length of the positive amplitude in a pulse wave.
Q - the bandwidth of a filter's resonance.
Quantize - the process of moving notes recorded into a sequencer to the closest time intervals specified by the user. Quantizing is used to correct rhythmic imperfections.
Release - the stage of a sound after a key is released. Sounds with a high release time end less abruptly than those with lower values.
Resonance - in filters, a function that reinforces frequencies near the filter-cutoff. Also used to refer to the Q setting. Resonance is perhaps what analog synthesis is best known for.
Sample - a digital waveform, or a patch made from such waveforms. Also, a single bit of digital audio information.
Sample-and-hold - modulation in fixed time intervals. The modulation can be random, or arpeggio-like.
Sampler - device that allows the user to create their own samples, or import samples created by others for use in composition and performance. This versatility has made samplers widely popular, and the method of choice for emulative synthesis.
Sample RAM - The amount of Random Access Memory present for storing samples in.
Sample Rate - in digital audio, the rate at which samples of the source sound are taken. Sample rate is most often expressed in kiloHertz (kHZ). The higher the sample rate, the higher the fidelity of the recording.
Sawtooth wave - basic waveform that contains all the harmonics in ever decreasing amplitude. It has a distinctive "buzzing" quality.
Sidebands - additional frequencies above and below the fundamental produced by FM synthesis.
Sinewave - the purest tone in sound, one of the basic waveforms. It contains no overtones.
Sequencer - device used to record and play back musical events, analogous to notation or piano rolls. Sequencers are used to control synthesizers to play music automatically to either accompany, or replace, the human performer.
Software Synthesis - any software program dedicated to producing synthetic sound. The term is most often applied to programs that can produce sound fast enough to be controlled via MIDI for performance or sequencer playback purposes.
Sound Module - a device designed solely to produce sound. It requires connection to a controller device to be played.
Square wave - a waveform with all odd harmonics. Technically it is a pulse wave with a duty cycle of 50%.
Subtractive - method of synthesis where frequencies are removed from a waveform rich in harmonics. Most methods in use today use subtractive synthesis via filtering.
Sustain - the stage of a sound that remains at a constant value after the decay as long as the key is depressed.
Sys Ex - diminutive for System Exclusive. This is information sent via MIDI intended to be used by only one device, but to be stored in another.
Theremin - Also known as the Etherovox, instrument invented in the 1920 by Lev Termin (Leon Theremin). The instrument is controlled by interruption of the energy field around a pitch antenna and an amplitude antenna. The player never touches the instrument during performance.
Tone Generator - term most often applied to Yamaha's FM sound modules.
Triangle wave - another of the basic waveforms. Contains odd harmonics in decreasing amplitude.
VCA - abbr.: Voltage Controlled Amplitude. The section of an analog synth that controls amplitude.
VCF - abbr.: Voltage Controlled Filter. The filter of an analog synth.
VCO - abbr.: Voltage Controlled Oscillator. The oscillator in an analog synth.
Velocity - the force with with a key is hit. In MIDI instruments, velocity can be expressed as a numerical value from 1-128.
Velocity sensitive - a keyboard that can record or transmit velocity information.
Voice - general term for either a single waveform or a single oscillator.
Waveform or Wave - the physical or digital shape of a sound.
Wavetable - a collection of samples stored in ROM. Also a synth containing such sounds.
Workstation - a combination of a controller keyboard, a sequencer, and a synthesizer. Many workstations include onboard effects processing.
Zero Crossing - point in a waveform where amplitude is at zero. Smooth loops should have beginning and end points at zero crossing.

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