Moog-music Slim Phatty User Manual download pdf (Page 70)

Page 72

Slim Phatty User’s Manual - Glossary

Page 73

Slim Phatty User’s Manual - Glossary

Glossary

Here are a few key terms that cover the basics of sound generation as used in the Little Phatty synthesizer.

ADSR – Abbreviation for Attack, Decay, Sustain and Release, the four stages of an envelope control voltage.

Amplitude – The strength of a sound’s vibration measured in Decibels (dB). Amplitude corresponds to the

musical term Loudness.

Continuous Controller (CC) – A type of MIDI message used to transmit control commands. These com-

mands are digital control signals for parameters such as volume, vibrato and panning.

Control Voltage – Control voltages (also called CVs) are used in analog synthesizers to affect changes in the

sound. In the case of pitch, pressing a key on the keyboard sends a control voltage that determines the

pitch of the oscillators. The keyboard CV is set to produce an equal tempered scale. As you play up the

keyboard, the CV is raised and the pitch increases. The pitch can also be affected by other CV sources,

like an LFO, often used to produce vibrato. Other major synthesizer components that respond to CV’s

include the lter (the higher the CV, the higher the lter cutoff frequency) and the amplier (the higher

the CV, the higher the gain, or volume).

Envelope – An envelope describes the contours that affect the characteristics of a sound (pitch, tone and

volume) over time. For example, when a string is plucked, its amplitude is suddenly very loud, but then

dies out gradually. This describes the Volume envelope of the sound. We observe that the initial part of

the plucked sound is very bright, but then the brightness fades away. This describes the Tonal envelope

contour. We also hear the frequency of the sound go slightly higher when the string is plucked, and then

drop slightly as the note fades. This is the pitch envelope contour. A synthesizer can create these kinds

of changes by applying electrically generated envelopes to oscillators (affecting pitch), lters (affecting

tone) and ampliers (affecting volume).

Envelope Generator – A circuit that generates an envelope signal. The envelope generator creates a time-

varying signal that can be applied to any voltage-controlled circuit. The Envelope Generators in the

Little Phatty have four adjustable segments: Attack, Decay, Sustain and Release, also sometimes referred

to as ADSR. The Attack, Decay and Release segments are specied as time parameters, while the

Sustain segment is a simply a level setting. Attack species the onset time of the envelope. For example,

the sound of a plucked string starts suddenly, meaning its volume envelope has a fast attack time. Decay

species how quickly the onset of the envelope fades into the sustained portion. Sustain is the level at

which the envelope sustains after the initial transient (the attack and decay portion). Finally, Release de-

termines how long the envelope takes to fade away. An Envelope Generator uses a trigger to start and

stop the ADSR envelope. This trigger is called a gate signal, and it’s produced whenever a key is pressed

on the keyboard. The gate signal turns on and stays on as long as a key is held down. When the key

is released, the gate signal turns off. When the gate is on, the Envelope Generator is triggered and the

envelope signal moves through the Attack and Decay segments and settles at the Sustain level as long as

the gate signal is on. When the gate goes off, the release segment of the envelope begins. A new gate

signal retriggers the Envelope Generator.

GLOSSARY

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Moog-music Slim Phatty User Manual Page 70