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Synth Sense


a dictionary of terms

ADSR: Attack, Decay, Sustain, Release, the sections of the most popular style of envelope generator.

ALGORITHM: Used by Yamaha to describe the patterns in which the sine wave oscillators of their DX synths are linked. The oscillators interact in different ways for many sound variations, dependent largely on those patterns.

ANALOGUE: The first form of synth electronics commercially developed, starting with the raw sound of an oscillator and treating it by various extra circuits (filter, envelope generator, etc). In recent digital synthesis, the synth works more as a calculator estimating what the sound would be if all those analogue circuits were working, and only giving those final instructions to the oscillators. This is why people sometimes say of digital synths that circuits such as the envelope generator exist in 'logic' or 'software' only... they're imagined.

ARPEGGIATOR: A bonus of using a microprocessor to control a keyboard is that it can either assign the top or bottom member of a group of notes to a single oscillator, or, if programmed, step through that group at a rate usually set by the LFO. This can be used to 'strum' a chord on a mono or poly synth producing an arpeggio.

ATTACK: The A in ADSR — the time taken for the sound to build from nothing to its maximum (slow for violins, fast for pianos).

AUTOTUNE: Automatically checks and retunes all a polysynth's oscillators to an internal standard.

BANDPASS: The name for a filter which cuts off the top and bottom frequencies of a sound, letting through the centre band only.

BYPASS: To sidestep one section of a synth and go on to the next.

CUTOFF: The frequency at which a filter will take effect allowing only the sound above or below it to pass.

CV: Control Voltage — that voltage which corresponds to a particular note on the keyboard. One volt per octave is the most common system. If middle C were equal to 3 volts, then the C octave above would be 4 volts, two octaves below, 1 volt, etc. Used when you want one keyboard to control the electronics of another synth. Such connections now standardised by MIDI.

DCO: Digitally Controlled Oscillator. The pitch is determined by digital commands, and not voltages as in VCOs. A more stable system.

DECAY: The D of ADSR — the first fall in volume, after the initial peak. Sustain is the level it drops to, Decay is the time it takes to get there.

DYNAMIC: As of keyboards, their ability to produce louder or brighter notes when you hit the keys harder.

ENVELOPE: The shape of a sound. How long it takes to achieve its maximum and minimum volumes.

FILTER: An electronic sieve that modifies the sound of a raw oscillator by stopping some frequencies and letting others through.

FOOTAGE: A measurement of octaves. A hangover from organ days when the longer was the pipe, so the lower was the note. 32 is low, 16 is an octave higher, 4 is three octaves higher. Can be used to describe other pitch intervals (5⅓ is a fifth), but less common today.

FREQUENCY: A measure of how high or low a tone actually is and which can be verified in a laboratory with instruments. Pitch is how high or low our brain tells us the tone is.

GATE: An instruction from a keyboard (or sequencer) that tells a note to get going. When a key is pressed down, the gate is on, when you release it, it goes off. Used alongside CV to control exterior synths, and likewise standardised in MIDI.

HI-PASS: A filter that lets through the high frequencies.

HOLD: When the synth remembers the last note played and keeps it going, even though you've taken your fingers off the keys.

KEYBOARD TRACKING: When the filter takes its example from the keyboard — the higher the note, the brighter it becomes; the lower the note, the more muted — useful since acoustic instruments often do it naturally. You can alter the amount or invert the direction.

LFO: Low Frequency Oscillator — an oscillator running at such a low frequency, you can't hear it as a note. It becomes a steady pulse, rising slowly or sharply, depending on the waveform, and can be used to modulate other departments of the synth (VCOs, filter, etc).

LINEAR/LOG: Mathematical laws. In the first, each step up the ladder is one bigger than the one before; in the second, each step is double what it was before. Log law oscillators are easier to control on the one volt per octave system because of that doubling characteristic. (A doubled pitch is one octave higher.)

LOW-PASS: A filter that lets through the low frequencies.

MIDI: Musical Instrument Digital Interface-the long awaited, but still slightly erratic standardised system for interconnecting synths.

MODULAR: Of instruments where the filters, envelope generators, etc are contained in separate, patchable boxes and not all under the same front panel.

MODULATION: Effects such as vibrato, wah-wah, etc, added to a sound, usually by an LFO.

MULTIPLE TRIGGER: When each new note you press triggers the filter and envelope generator again, regardless of whether your fingers are still depressing other keys. Single triggering involves lifting all your fingers off, before passing a new key.

NOTCH: A filter that removes only one frequency, ie a hum filter. Several notch filters cascaded together form a comb filter, better known as a Phaser or flanger.

OCTAVE: A group of eight notes that form the diatonic scale. An octave above means a note double the frequency.

OSCILLATOR: The primary sound source of a synthesiser. A circuit that switches on and off repeatedly and rapidly, so producing the electrical signal we hear as sound.

PARAMETER: One specific, self-contained segment of a synth-attack time, envelope amount, white noise volume, etc. Essential in modern synth programming where, to save money, one knob or button serves all the sections fixing the value of each parameter in turn.

PATCH: A pattern of connections and control settings that produce a particular sound, usually one you want to store in the synth's memory. Sometimes used to denote a pair of sounds (left and right hand).

PORTAMENTO: When the synth slides from the last note you played to the new one you're holding, instead of jumping instantly between them. Also known as Glide. Glissando is a similar effect but the synth picks out and plays every note in between during its journey.

PRESET: Unchangeable patches, usually set at the factory.

PROGRAMMABLE: Changeable patches, the user can alter the control settings and the synth will remember them.

PULSE-WIDTH: A characteristic of square waves measuring the time the oscillator is on (mark) against the time it's off (space) within one complete oscillation. If this mark/space ratio is 50/50 the quality of the sound will be rich and flutey, if it's 30/70 (or 70/30), the results will be brighter and reedier. If you continuously vary the pulse width with an LFO, one oscillator can be made to sound like two closely tuned to each other.

Q: Another term for Resonance.

RELEASE: The R of ADSR — the time taken for the notes to die to silence after you take your finger off the keys.

RESET: A control which chops a long release time to zero. Useful for sudden endings.

RESONANCE: The quality of a filter. Blowing over the top of a bottle gives a note. The bottle will sing at one note only — the resonant frequency. In a similar way, an electronic music filter can be peaked to ring at one frequency. The resonance control dictates how selective the filter is.

RIBBON CONTROLLER: A strip of conductive material which operates like a normal front panel rotary control but has been "unrolled". Instead of turning the control you run your finger along the ribbon. Looks flash.

RING MODULATOR: The circuit behind Dalek voices. It takes its name from the ring of four diodes between a pair of transformers used to build the device, before the days of integrated circuits.

The modulator has two inputs — the signal and the carrier. The output is the sum and difference between these frequencies and their harmonics. Sine waves can be used to give bell tones, but waveforms richer in harmonics can sound messy.

ROLL OFF: Another filter characteristic describing how steeply unwanted frequencies are cut back.

SAMPLE: Keyboards such as the Emulator and Fairlight listen to a sound and record it into their digital memory so it can be played back at any pitch. That recording, whether it be the complete sound or a short chunk of it, is known as the sample.

SAMPLE AND HOLD: A circuit which is fed a continuously changing voltage. When it's triggered by, say, pressing a key, it will instantly sample its input and hold the exact voltage being fed to it at that split second. A popular use is to feed it with white noise where every frequency is present, but shifting very fast. The sample will pick out a different, random frequency every time, and the speed of its selection is usually governed by the LFO.

SAWTOOTH: A signal waveform containing odd and even harmonics. Bright, often used for brass settings.

SECOND TOUCH: A facility occasionally found on dynamic keyboards. Once you've pressed a key to make a sound, pushing it down still harder will activate a switch and so introduce an effect such as modulation or pitch bend. On an expensive keyboard (DX1), every key will have its own switch, but most dynamic synths have one only that covers all the keys.

SEQUENCER: Tells the synthesiser what notes to play when your own fingers are otherwise engaged. Programmed in step time (precise mathematical divisions dependent on an internal metronome and entered bit by bit), or real time (listens to you playing the keys and remembers what you do).

SINE: A signal waveform containing no harmonics, just the fundamental. A bit dull to listen to but useful for modulation as it's so smooth.

SQUARE: A signal waveform containing only odd harmonics.

SUSTAIN: The S of ADSR. (See Decay.)

SYNC: A way of locking together two oscillators so one will always be at a fixed multiple of the frequency of the other. Sweeping one of them up and down in pitch will cause the harmonics of the other to try to follow it, producing the well known screaming or growling effect.

TRANPOSE: To shift the pitch, usually of the whole keyboard and most commonly up or down by an octave or two. Some synths will allow you to transpose in semi-tones so you could play a piece in B, but using the easy white note scale of C.

VCA: Voltage Controlled Amplifier — changes the volume of the sound you hear according to instructions from another section of the synth such as the ADSR Envelope Generator.

VCO: The earliest type of oscillator where changing voltages dictated its pitch. (See DCO.)

VOCODER: A device which analyses your voice (the modulator) and superimposes its characteristics (timbre, volume, etc) over the top of a synth sound (the carrier).

WAVEFORM: Each waveform has a particular profile determined by the number of harmonics it contains.. Harmonics are like copies of the basic 'fundamental' note but at multiples of the original frequency. For example, the second harmonic is an octave up from the original. Many harmonics can be mixed together and the blend determines the waveform. (See square, sawtooth, sine.)

WHEEL MOD: A control to introduce modulation, usually during performance. The further you push the wheel, the stronger the effect.

WHITE NOISE: Though it's predominantly used for wooshy surf and wind sounds, white noise actually contains a random mixture of all the frequencies the synth can produce. Pink noise is white noise with a bass boost.

X-Y CONTROLLER: Otherwise known as a joystick giving one handed control over two functions at once such as modulation speed and pitch bend.

X-Y MOD: The facility for the output of one oscillator to feed the voltage-controlled input of another and so cross modulate it. This can give very complex waveforms in the absence of a ring modulator.

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One Two Testing - Copyright: IPC Magazines Ltd, Northern & Shell Ltd.


One Two Testing - Nov 1984

Donated & scanned by: Mike Gorman

Synth Sense

Feature by Paul Colbert

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