User Guide

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one octave. The VCF CV is dropped 6 volts to –1 V. Notice that the cutoff frequency then drops 6
octaves, and at 250 Hz, only allows the fundamental tone through. Finally, the VCA CV is reduced
by 3 Volts. Notice the amplification is reduced to 40% of the maximum level.
Modulation - Modulation is the use of a CV to affect a voltage-controlled circuit. Modulation has a
source, destination, and amount. This could be as simple as the filter cutoff of a VCF (a modulation
destination) being changed by the front panel cutoff control (the source), or as complex as mixing
multiple CVs together to modulate filter cutoff. Modulation is used in synthesis to create complex
sounds and add variation.
Envelope Generator - An envelope describes the contours that affect the characteristics of a
sound as it evolves in time from its start to its finish. Take a plucked string for example: when a
string is plucked, its amplitude is suddenly very loud, then dies out gradually. The initial part of the
sound is very bright but then the brightness fades away. The frequency of the sound goes slightly
higher and then drops slightly as the note fades. These kinds of changes in a sound over time
can be applied to oscillators, filters or the amplitude of an electronically generated sound by an
envelope generator. The envelope generator creates a CV that describes the contours of a sound.