Operation Manual

4.7 The Vibrato Module 29
is divided into four phases, the Attack, Decay, Sustain and Release controlled by the A, D, S and R
controls respectively.
During the attack phase, the envelope signal goes from a value of zero to a value of 1 in a laps
of time controlled by the A knob. The decay phase then begins and the signal goes from 1 to the
sustain value of the signal in a laps of time controlled by the D knob. The level of the sustain
portion of the modulation signal is adjusted using the S knob. This value is held as long as a note
is depressed. Upon release of the note, the signal then decreases from its sustain value to zero in
a laps of time controlled by the R knob. The Delay knob of this module is used to add a delay
between the triggering of a note and the start of the envelope. This is useful to add noise to the
excitation signal following the initial impact noise from the Mallet module.
attack decay release
sustain
key pressed key released
1Volt
1Volt
Figure 10: ADSR Response curve.
4.7 The Vibrato Module
A vibrato effect is equivalent to a periodic low frequency pitch modu-
lation. This effect is generally obtained by using an LFO to modulate the
pitch signal of a signal generator. In Chromaphone, a dedicated module is
provided for this effect.
The Rate knob sets the frequency of the vibrato effect from 0.5 Hz to 5 Hz. The Amnt knob sets
the depth of the effect, or in other words the amplitude of the frequency variations. In its leftmost