Access os5 Manuale Utente

CHAPTER 4

Introduction

highly desirable that your box is silent. With the
filter envelope, the situation is somewhat differ-
ent: It always starts at the Cutoff value that you
determined manually. And it is definitely not al-
ways desirable that the fi lter frequency is
brought to the maximum level.

Consequently, you need a tool that limits the ef-
fective range of the fi lter. This is why we
equipped the VIRUS with a control labeled ENV
AMOUNT (short for Envelope Amount). When
the pot is turned counter-clockwise to the far
left, the filter has no effect on the cutoff fre-
quency; the further you turn the pot to the right,
the greater the effect the filter envelope has on
the filter frequency. The maximum level of the
envelope may lie outside the audible range
when the filter has already been partially
opened via the Cutoff pot or was manipulated
via other control options. In extreme cases
where the filter is already completely open, the
filter frequency cannot be increased regardless
of how high you set the ENV AMOUNT.

Go ahead and spend some experimenting with
different ENV AMOUNT, Cutoff and RESO-
NANCE settings for the diverse filter operating
modes. Also try varying the settings for the am-
plifier envelope. You will find that with just these
few parameters you are able to come up with a
vast amount of sound settings. If you ar e
among the many musicians who are associative
listeners, you might say many of the settings
produce sounds reminiscent of stringed-instru-
m e n t s ; s o m e s o u n d p i c k e d , p l u c k e d o r
snapped, others sound bowed.

For your next experiment set the amplifier enve-
lope so that you hear a constant level when you
press and hold a note. Now deactivate the filter
envelope by setting the ENV AMOUNT to 0. Set
Filter-1Filter-1 to low pass mode and decrease
the filter frequency until you just barely hear a
muddy signal when you play notes in the mid-
range.

Now play a few higher and lower notes. You will
find that the lower notes have a greater over-
tone content, whereas the higher notes sound
muddier and their volume decreases until the
notes are completely inaudible. You might al-
ready suspect what this is all about: As the
notes are transposed ever lower, more portions
of the signal fall below the cutoff frequency,
whereas with the notes that are transposed ev-
er higher, more portions of the signal rise above
the cutoff frequency and subsequently are sup-
pressed until the root note and the last audible
portion of the signal is silenced.

To avoid this effect - or if desirable, to amplify it
- you have the option of influencing the cutoff
frequency via the pitch of the note, i.e. the note
number. The degree of influence is determined
by the KEY FOLLOW. You find this parameter
within the Filter Edit menu.

Please note that KEY FOLLOW is a so-called
bipolar parameter: Its control range is not limit-
ed to the positive end of the spectrum (0 to a
maximum of 127). Bipolar controls effect nega-
tive values as well, in this case from the nega-
tive maximum of -64 through 0 an on to the
positive maximum of +63. Consequently, if this
pot is set to the center position (12 o’clock or 0)
the pitch of the notes corresponding to the keys
on your keyboard has no effect on the cutoff
frequency. If on the other hand you turn the KEY
FOLLOW pot clockwise towards the positive
control range, you will find that the filter opens
up increasingly as the pitch increases with high-
er notes. At lower notes, the filter closes down
again. If you turn the pot counter-clockwise to-

-100%

100%

CUTOFF

RESONANCE

ENV AMOUNT