Software Synthesizer Vocabulary

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Whether you use VSTi, DXi or standalone and modular applications, this seemingly nonsense nomenclature needs some serious explaining

Surely youíve glanced across the shiny GUI displays, mesmerized by a myriad of buttons, knobs and switches, but what are they all for? Whether you use VSTiís, DXiís or standalone and modular applications, this seemingly nonsense nomenclature needs some serious explaining. LFOs, VCFs, ADSRs? Oscillators and low pass filters, portamento and vibrato. Is this science class or a menu at an Italian restaurant? Neither! This is the wonderful world of software synthesizers, or softsynths for short. And at first it may all seem like rocket science, but never fear, softsynths are a stellar addition to any digital audio workstation, and learning to use them is blast!

This article will focus on the vocabulary behind software synthesis, and delve lightly into the basics on how you can use each feature to work for you! In other words, this hasnít been written with intention for the viewer to read through from top to bottom, although you very well may do so. This is more of a dictionary of digital synth jargon. Looking for a particular term? Just scroll down through the alphabetically organized list looking for related terms and multiple meanings. Still lost? Then feel free to post a message in the HRC forums and someone there will be glad to help out!

ADSR - Attack, Decay, Sustain, Release. An ADSR envelope is a modulation envelope determines the amount of amplitude (volume) or other modulation the sound will have at different times throughout a noteís duration. The initial onset of the sound at the time the note is triggered is determined by the A or Attack. Using amplitude as an example, the roar of the ocean crashing on the beach has a slow onset as it gently rises in volume over time. In contrast, the whack of a snare drum comes suddenly and reaches it maximum volume within milliseconds. Closely related to attack is decay. Decay determines how long the maximum volume of the initial onset is maintained and how long it takes to settle in at the sustain volume.. A longer decay means the note will stay loud longer. Sustain and release are important in determining whether or not the sound will continue to exist after the initial attack and decay. A piano for instance will continue to sustain a note for a long time if the key remains depressed, and even longer if the player has depressed the sustain pedal. While a typical piano note will eventually quiet and fade out, a childís toy synth may sustain onwards forever so long as the key is depressed. Release tells the synth how long to allow the note to play even after the note has been turned off. For instance, a big crash cymbal sounds out long after the drummer has struck it and moved on to striking other instruments. Note that ADSR envelopes can also be applied to filters and other modulations, not just amplitude, it all depends on the synth.

Amplitude - The loudness of a sound is determined by itís amplitude. This is how high and low each oscillation of the waveform peaks. Amplitude can be called "amp", "level:, "gain", and "volume". Generally it is better to turn down a loud oscillator or synth than turning up a quiet one.

Analog - Sometimes spelled analogue, this is anything not digital. Vinyl records and cassette tapes are examples of analog audio storage. In the software synth world everything is digital, but youíll hear the word over and over again. Analog describes the hardware synths that use varying voltages to produce rich and textural sound, as opposed to the dry and lifeless sound usually associated with digital synths. For this reason many softsynth developers claim that their products are "modeled after analog synths" or that they produce that "warm analog" sound. And the truth is, many do! Analog is antonymous to digital.

Attack, Att or Atk *see ADSR*

Bassline - The low-end synthesizer sound that shakes the dance floor. A bassline is the general term given to any low frequency and often repetitive synth line. The stereotypical bass is rhythmic and makes you want to dance. Some tricks to getting that classic club bass sound are low-pass filters and bass boost. Apply LP filter to cut out any treble and really round off your sound, and try different cut-off settings to find the tone you are looking for. If your bassline still lacks presence, try to boost the low frequencies with a little EQ. Watch your levels (volume); low frequency sounds have large waveforms and can quickly cause your whole mix to distort. See also *Lead* and *Pad*

BP - Bandpass filter *see Filters*

BPM *see Tempo*

Chorus - A modulation effect similar to flange sometimes found on a softsynth that gives the effect of there being many instruments playing at once, as if a whole chorus were performing. Many offer an LFO, a pan and a feedback control. Use chorus to give your synth lines presence and organic depth.

Cutoff or Cut *see Filters*

Decay or Dec *see ADSR*

Delay - An effect sometimes found on a softsynth. Delay causes the output signal to occur late, opening up all sorts of possibilities for thickening your sound. There are usually several parameters provided to manipulate the output of the effect. "Time" adjusts how frequently the input is resampled while "feedback" controls how many times the sample is repeated. "Diffusion" or "spread" allows you to place the echoes all across the stereo field, while "level", "amount", or "mix" adjusts the effectís overall output volume. There are two basic kinds of delay: reverberation and echo. Reverb is the fast kind and gives your output a brightening bath of quick echoes that tattoo off into the distance. Echo is the same thing, only much slower. A well timed echo can turn a dull rhythm or dry synth lead into a searing hit hook.

Digital - Anything that breaks data up into tiny pieces is digital. The opposite of digital is analog. Computers work on a binary or "two value" system. All of the data your computer processes is broken down into bits, the smallest form of data a computer can handle, each of which can have only two possible values; 1 or 0, yes or no, true or false. A good way to describe it is to compare an old vinyl record with one of todayís compact discs. The data stored on a vinyl record is an infinitely varying representation of a waveform etched into the plastic disc as a bumpy groove. If you could view a record under a microscope you could see all the hills and valleys of the waveform with small and quick ripples being the higher frequencies and the larger wider mountains being the lower frequencies. A compact disc differs in that itís data has been encoded into a binary digital format. If you could view that CD under a microscope you would see that only two kinds of data have been stored. The tracks of the disc would been separated into bits that would either been burnt by the laser or not, either a one or a zero. Every 16 bits of data would represent 1 digital sample, or snapshot, that the CD player or sound card must decode from 1ís and 0ís back into an analog signal before it is sent to your speakers. The other major difference between digital and analog is rooted in digital audioís 1ís and 0ís format. Since data is transferred as very precise bits, with each bit being a 1 or a 0, there is absolutely no quality loss when you make a copy or transfer the file to another location.

Distortion - An effect sometime found on a softsynth. Distortion means mean things in the audio world. Distortion is the name given to the undesirable effect of a loud audio signal "clipping" when it peaks. But as any guitarist knows, sometimes this "clipping" can be a useful tool in shaping your instrumentís tone. Controlled distortion, also called overdrive, boosts the signal beyond its mechanical limits causing the peaks of the waveform to be chopped off giving it that hard and grindy feel like a heavy metal guitar. Use this effect to add a harsh edge to your sound, but watch your volume! Too much gain and overdrive can cause your whole mix to distort. Unless thats the sound your going for?

Echo - A type of delay. *see Delay*

Envelopes - Envelopes define how a synthesizerís parameters will be applied over time. For instance a VCA, or voltage controlled amplifier, is an envelope that determines how much volume there will be at different points in the notes duration. The two most common types of envelopes are graphic envelopes and ADSR envelopes. A graphic envelope is a powerful x,y, multi-pole barchart that lets you draw, usually by mouse, the envelope in a simple connect-the-dot style fashion. You may be familiar with graphic envelopes on equalizers. ADSR envelopes are much more simple with only four parameters controlling the shape. Envelopes can be applied to almost any parameter, depending on the synth. The most common envelopes modulate the amplitude and filter. See *ADSR*

Filters - Imagine a filter, sometimes referred to as VCFís or voltage controlled filters, as a special kind of equalization. It lets you "filter" out specific frequency ranges. Which frequencies are quieted are determined by the "cut" or cutoff point and type of filter. The cutoff is the frequency where the "cut" or reduction begins. To understand what happens at the "cut" it help to understand the different types of filters. The two most common types of filters are high-pass (HP) and low-pass (LP) filters. With a high-pass filter, all the frequencies below the cutoff are reduced thereby allowing the highs to pass through unaffected. The opposite occurs in a low-pass filter where all the frequencies above the cutoff are reduced; in a low-pass filter the lows are allowed to pass. Another common type of filter is the bandpass (BP) filter, sort of a combination of both a high-pass and low-pass filter, where a specific "band" or range of frequencies are allows to pass and the frequencies above and below that band are cut. A "Q" knob is usually available to let you choose the width of that band. A "Q" may also affect the filterís resonance. Sometimes a filter can be triggered by an LFO or envelope. In the latter an ADSR envelope is often used. In that case there is usually a "ENV" amount knob the adjust how much envelope is to be applied. Note that sometimes the cutoff frequency will be labeled "freq" instead of "cut" and the "cut" will actually be the amount of reduction. Every synth is different. Some synth let you choose between a couple preset amounts of reduction, usually labeled in negative decibels (-dB). Filters are a great way to entirely change the effect a sound has on a listener.

Flange - A modulation effect found on some software synths. Flange creates a chorus-like swirl in the output similar to the effect of a phase shifter, but not as "over-the-edge". Like phase shift and chorus, flange usually has parameters controlling LFO frequency and depth as well as effect feedback and wet/dry mix. Add flange to the output of your synth to give a colorful suggestion of movement.

Glide - Same as portamento. A synth with glide allows notes that occur in close proximity in time to sliiiiiide together making a smooth sweep up or down in pitch. See *Portamento*

HP - High-pass filter *see Filters*

Interpolation - The mixing of multiple waveforms. Anytime two or more sounds are mixed together, the computer has to figure out what the resulting waveform will sound like. The process is called interpolation and it occurs on many levels throughout the digital audio production process, from the synthesizer adding two oscillators together all the way up to the final mixdown in your multi-tracker. The mathematical algorithm used to mix the sounds is what determines the output quality and is generally given in bit-depth. The higher the bit-depth the more accurate the mix.

Lead - In hardware synths a lead is a wire or a path on a circuit board, but here Iím talking about lead synth, just like lead guitar, or lead vocals. In sequencing and performance, when we say lead synth, we mean the up-front, often bright and expressive lines being played, generally melodic and contrasting with the rhythm. Lead lines are usually characterized by obvious and in-your-face keys strokes and a fast attack in the amplitude envelope. Need to spice up a lead line? Add some distortion and/or delay to bring the synth forward in the mix. Also, try tweaking your synthís filter cutoff point while the song is being played for a classic filter sweep effect. See also *Bassline* and *Pad*

LFO - Low Frequency Oscillator. Just like it says, an oscillator designed to generate a subsonic waveform to be used to control another feature. The waveform created isnít heard. Instead it is used to modulate other parameters such as filter cutoff, pitch, etc. Depending on the synth you may or may not be able to assign the LFO to certain parameters. There will be a "speed" or "rate" parameter that controls how fast the oscillator moves and possibly even an "amount" or "level" knob to choose the amplitude. The LFO is usually a perfect sine wave unless otherwise stated. You may even have the option to choose a square or triangle wave. Try this: use LFOs to trigger automatic changes in cutoff for a classic breathing synth effect.

LP - Low-pass Filter *see Filters*

MIDI - Musical Instrument Digital Interface. MIDI is an old standard in digital audio, originally created as a standardized set of commands that could be sent from one hardware machine to another. This would allow musicians to link up different controllers and sound modules to produce unique sounds and to allow MIDI sequencers to trigger the other hardware in exactly the same way each time a piece was performed. In todayís world of software synthesis we still often use MIDI code to allow two pieces of software to communicate with each other in a standardized language. VSTiís for instance use MIDI data to communicate with their host applications. MIDI data does not actually contain any actual audio, only simple commands, and is therefor very small in size. The data may consist of, but is not limited to, a note on signal that triggers the note, pitch data, velocity, pan, and a note off signal to tell the note when to stop.

Modular - Softsynths that can be constructed, usually within their own standalone application, and have their individual parts added to and reconnected however the user wishes is called a modular synth. These synths may very well be the most powerful of the softsynths since the experienced user can build their own instrument from the ground up.

Modulation - This term has many uses in the digital audio field. Quite simply it means to "change" or "alter", for instance the way an LFO linked to the filter cutoff frequency causes the synth to breath and shift about. The word is also often heard when describing FM, or frequency modulation. This is a method of audio synthesis in which one oscillator affects another. Modulation also refers to some types of signal processing, such as flange, phase shift, and chorus.

Monophonic *see Polyphony*

Octave or Oct - The distance you travel in pitch when the pitch has doubled in frequency. For example the following notes are the first 6 Aís on the keyboard: 55Hz, 110Hz, 220Hz, 440Hz, 880Hz, and 1760Hz. Some synths allow you to transpose pitch an entire octave at a time. *see Pitch*

Oscillators - Also called "oscís", VCOís, or voltage controlled oscillators, oscillators are the heart of a synthesizerís waveform creating potential. Many softsynths allow the user to choose between a number of preset waveforms called shapes including the naturally smooth and warm sounding "sine" wave, and more coarse or harsh sounding "saw", "square" and "triangle" waves. Some synths even allow you to load up your own user-definable waveform from a sound file of your choice. Multiple oscillators allow for more complex sounds. In additive and subtractive synthesis each oscillatorís waveform is interpolated, or mixed together, to form a final product. In frequency modulation (FM) each oscillator directly affects the next in a chain. A general rule is, the more oscillators, the more organic and realistic sounding the output can be. Additional parameters for each oscillator can include "coarse pitch", "fine pitch", and "level" to name a few. The pitch adjusting options allow you to correct for differences in key or to add complex harmonics to your output. Level, amplitude, or mix knobs let you choose which oscillators are more prominent in the final mix by controlling their volume. Some special oscillators include LFOís and "sub" oscillators that produce very low frequencies and "noise" oscillators that produce random information to add a static treble effect. The start point of the waveform can sometimes be chosen by adjusting the "phase". Turning the phase all of the way in the opposite direction totally inverts the output waveform.

Overdrive *see Distortion*

Pad - Pad can mean several things in the audio world. For instance, the term can be used as a verb or a noun meaning to quiet something or something that quiets. That pads we are talking about are a generalized type of synth line. Pads are the long and blanketing notes heard in many forms of electronic music that seem to fill in the empty spots in a song and raise the whole mix to heavenly places. A pad usually lasts at least an entire measure, if not for several and can really make the difference between a weak song and club hit. Some good tricks for getting a typical pad sound out of your synth are high-pass filter and a slow attack. Timbre is everything in a synth pad, and choosing the right sound is essential, as in any synth line. A HP filter can help you cut out the intrusive low end and separate the line from your drum tracks. The more treble and sparkle the better. Also, try increasing the attack time on the amplitude envelope for a breathy, slow-rising pad typical of todays electronic music. See also *Lead* and *Bassline*

Pan - Panorama describes how the output sits in the stereo field. Center, left, and right should be clearly marked on the dial. Hard left and the signal is strongest in the left channel and silent in the right. Hard right and vice versa. A centered pan will be equal in both channels. This is usually something left for the final mixdown process, but thatís a whole Ďnother tutorial!

Phase - Like the phases of the moon, an audio waveform goes through cycles beginning at the zero crossing and heading outwards towards the edge of the possible field, then turning back and crossing the zero line heading out towards the opposite edge and finally returning to the zero line to do it again. At which point along this cycle the oscillator begins its modulations is determined by the phase setting. Generally this is not necessary, but when mixing many different waveform together, sometimes the phase of some of those sound sources need to be adjusted to ensure that resulting interpolation of sounds arenít canceling each other out. On a smaller scale, sometimes pushing some of your oscillators out of phase causes interesting harmonics as the in-phase waveforms mingle with them.

Phase Shift - A phase shifter is a modulation effect found on some softsynths which sway the output back and forth in phase based on the frequency (rate) and amplitude (depth) of an LFO. Add a phase shifter, also called a phaser, to give your synth an out-of-this-world sound.

Pitch - This is how high or low a tone is. Some generalized ranges of pitch include bass, mids, and treble. If your softsynth has a pitch control on it, this is used to detune or raise the pitch of the notes being played. "Coarse" and "Transpose" all will adjust the output pitch by a large factor, usually 1 semitone. "Fine" does just what it says, adjusting in tiny increments, usually in cents of a semitone. A setting marked "Octave" on a synthesizer shifts the entire output pitch by a whole octave or 12 semitones. Some highend synths offer a pitch wheel just like the hardware synths, which you can rock back and forth and will return to its home position when you let go, allowing you to pitch bend the output into oblivion.

Polyphony - Polyphony means "many sounds" and tells just that; how many simultaneous notes a synth can play or is playing. Polyphony is usually stated in powers of two. 1, 4, 16, and 32 are common values of polyphony. The simplest synths are monophonic, meaning they can only produce one sound at a time. If a monophonic synth is playing one note, and then it is sent the command to play another, the previous note is cut off so as to allow the next to play. Naturally you need more polyphony to play chords and complex passages, but more polyphony also means more memory and CPU use. Sometimes you can free up computer resources by trimming back the "poly" setting in your synth. Polyphony may also be called "voice", as in "64-voice".

Portamento - From the Italian word for travel, this is when a note rises or falls from one pitch to another. Some softsynths, especially monophonic bassline and lead type synths, offer the option to turn this great feature on or off and allow you to choose the rate of travel. Portamento is often called glide.

Presets - Presets are saved parameter settings that allow you recall a previous configuration. Its usually a good idea once youíve dialed up that sweet sound you were looking for to save it as a preset in case you need to come back to it later. Some synths come with factory presets; configurations that the manufacturer included to give you an example or what the product is capable of. Not all softsynths offer built in preset functions, but most external hosts (VSTi hosts for instance) allow a parameter dump that can be recalled later.

Release or Rel *see ADSR*

Resonance - Res causes the signal to resonate at a certain frequency, a sound usually associated with the techno and dance club scene. To achieve this sound the frequencies near the cutoff frequency are boosted simulating the effect of an instrument resonating at that frequency. The amount of resonance can usually be adjusted with a knob labeled "res" or "rez". The width of the excited frequency is usually adjusted with a "Q" parameter. A filter with the option to add resonance is sometimes called a "rezofilter" and can completely change the feel of synthís output. Try slowly sweeping the cutoff point up and down while the resonance is turned up to get that familiar analogue synth filter effect. Turn the "Q" all the way up experience whatís know as "self-oscillation" where only the cutoff frequency gets through overpowering the rest of the signal!

Reverb - Reverberation. A type of delay. *see Delay*

Sequencer - This is the portion of your software setup that chooses when each note will be played, when to play it and for how long. This is a little off topic, so Iíll just touch on a few facts. Sometimes called a step sequencer this is what makes the production of electronic music possible. Sequencers began decades ago as MIDI triggers that connected to other MIDI devices such as keyboard synths, drum machines and samplers. When the pre-recorded sequence was played back, the sequencer would send MIDI data to each device making a one-man performance possible. Nowadays the software sequencer allows for controlled triggering of synth notes and samples. You will need some form of sequencer unless you intend to perform and record entirely in "real-time".

Stereo - Having two separate audio channels; A left and a right. *see Pan*

Sustain or Sus *see ADSR*

Tempo - The speed of a musical piece measured in beats per minute (BPM). This is usually a setting in your sequencer.

VCA - Voltage Controlled Amplifier. *see Envelope*

VCF - Voltage Controlled Filter. *see Filters*

VCO - Voltage Controlled Oscillator. *see Oscillators*

Velocity - This is how hard a note is played. It determines how loud that noteís output is. Each note can have itís own velocity. The higher the velocity the more emphasis is placed on that note. This usually applies only to virtual instruments that handle MIDI data. You can usually find settings for velocity within your sequencer.

An effect found on some softsynths that quickly modulates the pitch causing a tremolo effect on the output. This effect can be emulated by linking an LFO to a softsynths pitch control and allowing the LFO to modulate it.

Corrections or amendments, feel free to contact me from my personal profile.

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User-submitted comments

Nur Nachman
Apr 09, 2005 05:04 pm
great article

good to refresh

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