Alesis ModFX Reference Manual page 36

3
Using the Philtre
Envelope
Like Trigger, Envelope modulation takes its cue from the input
signal instead of using a periodic wave. In Envelope mode, the
filter frequency follows the average amplitude envelope of the
incoming signal—the louder you play, the higher the filter
frequency will move. Envelope is used in "auto-wah" effects, and
for making dynamics more pronounced.
How quickly the filter responds to level changes in the incoming
input is controlled by the [RATE] knob. The most obvious effect
of the [RATE] control is to slow down the attack time of the
envelope. In this sense, Envelope is the opposite of Trigger: on
similar inputs, Envelope "swoops up" where Trigger would
"swoop down". However, it's actually more complex than that.
Think of the [RATE] control as being a "shock absorber" on how
quickly the filter frequency will follow the changes in level of
incoming sound. At low [RATE] settings, the filter responds
slowly, both up and down. At midrange settings, it more quickly
moves, in sync with individual notes. At the highest range, the
filter almost jitters as it tries to follow the envelope of the
incoming signal exactly.
In this mode, TEMPO SYNC/TAP TEMPO features have no
effect.
34
Rate settings are the
key to Envelope mode
At lo w [ RATE] s ettin gs , the
filte r will g ra du ally op e n up
o nly if yo u p la y se v er al no te s
in a ro w—lik e y ou we re
tur ning an EQ k no b d ur in g a
c re sc en d o. Abo ve th e "1 2
o 'c lo ck " s ettin g, th e en v elop e
will fo llo w e ac h no te, m a king
the c ha r ac te r is tic "an alo g
s yn th es ize r" so un d.